docs(chore): Normalize for consistency (#2206)

"Brief" summary/overview of changes. See the PR discussion or individual commits from the PR for more details.

---

Only applies to the `docs/content/**` content (_and `setup` command_). `target/` and `test/` can be normalized at a later date.

* Normalize to `example.com`

- Domains normalized to `example.com`: `mywebserver.com`, `myserver.tld`, `domain.com`, `domain.tld`, `mydomain.net`, `my-domain.tld`, `my-domain.com`, `example.org`, `whoami.com`.
- Alternative domains normalized to `not-example.com`: `otherdomain.com`, `otherdomain.tld`, `domain2.tld`, `mybackupmx.com`, `whoareyou.org`.
- Email addresses normalized to `admin@example.com` (in `ssl.md`): `foo@bar.com`, `yourcurrentemail@gmail.com`, `email@email.com`, `admin@domain.tld`.
- Email addresses normalized to `external-account@gmail.com`: `bill@gates321boom.com`, `external@gmail.com`, `myemail@gmail.com`, `real-email-address@external-domain.com`.
- **`faq.md`:** A FAQ entry title with `sample.domain.com` changed to `subdomain.example.com`.
- **`mail-fetchmail.md`:** Config examples with FQDNs for `imap`/`pop3` used `example.com` domain for a third-party, changed to `gmail.com` as more familiar third-party/external MTA.

* Normalize config volume path

- Normalizing local config path references to `./docker-data/dms/config/`: `./config/`, `config/`, \``config`\`, `/etc/` (_volume mount src path prefix_).
- Normalize DMS volume paths to `docker-data/dms/mail-{data,state,log}`: `./mail`, `./mail-state` `./data/mail`, `./data/state`, `./data/logs`, `./data/maildata`, `./data/mailstate`, `./data/maillogs`, (_dropped/converted data volumes: `maildata`, `mailstate`_).
- Other docker images also adopt the `docker-data/{service name}/` prefix.

* `ssl.md` - Use `dms/custom-certs` where appropriate.

* Apply normalizations to README and example `docker-compose.yml`

---

Common terms, sometimes interchangeably used or now invalid depending on context: `mail`, `mail container`, `mail server`, `mail-server`, `mailserver`,`docker-mailserver`, `Docker Mailserver`.

Rough transformations applied to most matches (_conditionally, depending on context_):

- 'Docker Mailserver' => '`docker-mailserver`'
- 'mail container' => '`docker-mailserver`' (_optionally retaining ' container'_)
- 'mail server' => 'mail-server' / '`docker-mailserver`'
- 'mail-server' => '`docker-mailserver`'
- 'mailserver' => 'mail-server' / '`docker-mailserver`'

Additionally I checked `docker run` (_plus `exec`, `logs`, etc, sub-commands_) and `docker-compose` commands. Often finding usage of `mail` instead of the expected `mailserver`

Additionally changes `mailserver` hostname in k8s to `mail` to align with other non-k8s examples.

---

* drive-by revisions

Mostly minor revisions or improvements to docs that aren't related to normalization effort.

docs/content/examples/tutorials/mailserver-behind-proxy.md

@@ -1,5 +1,5 @@
 ---
-title: 'Tutorials | Mailserver behind Proxy'
+title: 'Tutorials | Mail-Server behind a Proxy'
 ---
 
 ## Using `docker-mailserver` behind a Proxy
@@ -23,17 +23,17 @@ Luckily `dovecot` and `postfix` are both Proxy-Protocol ready softwares so it de
 
 The configuration depends on the used proxy system. I will provide the configuration examples of [traefik v2](https://traefik.io/) using IMAP and SMTP with implicit TLS.
 
-Feel free to add your configuration if you archived the same goal using different proxy software below:
+Feel free to add your configuration if you achieved the same goal using different proxy software below:
 
 ??? "Traefik v2"
 
     Truncated configuration of traefik itself:
 
     ```yaml
-    version: '3.7'
+    version: '3.8'
     services:
       reverse-proxy:
-        image: traefik:latest
+        image: docker.io/traefik:latest # v2.5
         container_name: docker-traefik
         restart: always
         command:
@@ -54,16 +54,16 @@ Feel free to add your configuration if you archived the same goal using differen
     [...]
     ```
 
-    Truncated list of necessary labels on the mailserver container:
+    Truncated list of necessary labels on the `docker-mailserver` container:
 
     ```yaml
     version: '3.8'
     services:
       mailserver:
         image: docker.io/mailserver/docker-mailserver:latest
+        container_name: mailserver
         hostname: mail
         domainname: example.com
-        container_name: mailserver
         restart: always
         networks:
           - proxy
@@ -98,20 +98,20 @@ Feel free to add your configuration if you archived the same goal using differen
 
 The following changes can be achieved completely by adding the content to the appropriate files by using the projects [function to overwrite config files][docs-optionalconfig].
 
-Changes for `postfix` can be applied by adding the following content to `config/postfix-main.cf`:
+Changes for `postfix` can be applied by adding the following content to `docker-data/dms/config/postfix-main.cf`:
 
 ```cf
 postscreen_upstream_proxy_protocol = haproxy
 ```
 
-and to `config/postfix-master.cf`:
+and to `docker-data/dms/config/postfix-master.cf`:
 
 ```cf
 submission/inet/smtpd_upstream_proxy_protocol=haproxy
 smtps/inet/smtpd_upstream_proxy_protocol=haproxy
 ```
 
-Changes for `dovecot` can be applied by adding the following content to `config/dovecot.cf`:
+Changes for `dovecot` can be applied by adding the following content to `docker-data/dms/config/dovecot.cf`:
 
 ```cf
 haproxy_trusted_networks = <your-proxy-ip>, <optional-cidr-notation>