docs(ci): Add versioning support without using 'mike'

It seems it may have be simpler to just use 'mike'..

Additionally squashes related commits providing minor fixes + improvements:

- Use a job dependency (`needs`) to avoid `push` event race conditions due to parallel jobs.
- Improve workflow file documentation via inline comments.
- Make ShellCheck linting happy.
- `chown` doesn't seem to work unless on the default branch for CI. Opted to use the docker `--user` approach instead.

.github/workflows/scripts/docs/update-versions-json.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+# CI ENV `GITHUB_REF` from Github Actions CI provides the tag or branch that triggered the build
+# See `github.ref`: https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#github-context
+# https://docs.github.com/en/actions/reference/environment-variables
+function _update-versions-json {
+  # Extract the version tag, truncate `<PATCH>` version and any suffix beyond it.
+  local MAJOR_MINOR
+  MAJOR_MINOR=$(grep -oE 'v[0-9]+\.[0-9]+' <<< "${GITHUB_REF}")
+  # Github Actions CI method for exporting ENV vars to share across a jobs steps
+  # https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#setting-an-environment-variable
+  echo "DOCS_VERSION=${MAJOR_MINOR}" >> "${GITHUB_ENV}"
+
+  if [[ -z "${MAJOR_MINOR}" ]]
+  then
+    echo "Could not extract valid \`v<MAJOR>.<MINOR>\` substring, exiting.."
+    exit 1
+  fi
+
+  local VERSIONS_JSON='versions.json'
+  local IS_VALID
+  IS_VALID=$(jq '.' "${VERSIONS_JSON}")
+
+  if [[ ! -f "${VERSIONS_JSON}" ]] || [[ -z "${IS_VALID}" ]]
+  then
+    echo "'${VERSIONS_JSON}' doesn't exist or is invalid. Creating.."
+    echo '[{"version": "edge", "title": "edge", "aliases": []}]' > "${VERSIONS_JSON}"
+  fi
+
+
+  # Only add this tag version the first time it's encountered:
+  local VERSION_EXISTS
+  VERSION_EXISTS=$(jq --arg version "${MAJOR_MINOR}" '[.[].version == $version] | any' "${VERSIONS_JSON}")
+
+  if [[ "${VERSION_EXISTS}" == "true" ]]
+  then
+    echo "${MAJOR_MINOR} docs are already supported. Nothing to change, exiting.."
+    exit 1
+  else
+    echo "Added support for ${MAJOR_MINOR} docs."
+    # Add any logic here if you want the version selector to have a different label (`title`) than the `version` URL/subdirectory.
+    local TITLE=${TITLE:-${MAJOR_MINOR}}
+
+    # Assumes the first element is always the "latest" unreleased version (`edge` for us), and then newest version to oldest.
+    # `jq` takes the first array element of array as slice, concats with new element, then takes the slice of remaining original elements to concat.
+    # Thus assumes this script is always triggered by newer versions, no older major/minor releases as our build workflow isn't setup to support rebuilding older docs.
+    local UPDATED_JSON
+    UPDATED_JSON=$(jq --arg version "${MAJOR_MINOR}" --arg title "${TITLE}" \
+      '.[:1] + [{version: $version, title: $title, aliases: []}] + .[1:]' \
+      "${VERSIONS_JSON}"
+    )
+
+    # See `jq` FAQ advising this approach to update file:
+    # https://github.com/stedolan/jq/wiki/FAQ
+    echo "${UPDATED_JSON}" > tmp.json && mv tmp.json "${VERSIONS_JSON}"
+  fi
+}
+
+_update-versions-json