Added psalm to dev dependencies.

symfony.lock

@@ -1,7 +1,16 @@
 {
+    "amphp/amp": {
+        "version": "v2.2.1"
+    },
+    "amphp/byte-stream": {
+        "version": "v1.6.1"
+    },
     "clue/stream-filter": {
         "version": "v1.4.1"
     },
+    "composer/xdebug-handler": {
+        "version": "1.3.3"
+    },
     "doctrine/annotations": {
         "version": "1.0",
         "recipe": {
@@ -96,6 +105,12 @@
     "egulias/email-validator": {
         "version": "2.1.7"
     },
+    "felixfbecker/advanced-json-rpc": {
+        "version": "v3.0.4"
+    },
+    "felixfbecker/language-server-protocol": {
+        "version": "v1.4.0"
+    },
     "fig/link-util": {
         "version": "1.0.0"
     },
@@ -132,6 +147,9 @@
     "monolog/monolog": {
         "version": "1.24.0"
     },
+    "netresearch/jsonmapper": {
+        "version": "v1.6.0"
+    },
     "nikic/php-parser": {
         "version": "v4.2.1"
     },
@@ -165,6 +183,9 @@
             "./config/packages/datatables.yaml"
         ]
     },
+    "openlss/lib-array2xml": {
+        "version": "1.0.0"
+    },
     "php-http/curl-client": {
         "version": "2.0.0"
     },
@@ -231,6 +252,9 @@
     "s9e/text-formatter": {
         "version": "1.4.1"
     },
+    "sebastian/diff": {
+        "version": "3.0.2"
+    },
     "sensio/framework-extra-bundle": {
         "version": "5.2",
         "recipe": {
@@ -647,9 +671,18 @@
     "twig/twig": {
         "version": "v2.6.2"
     },
+    "vimeo/psalm": {
+        "version": "3.5.1"
+    },
     "webmozart/assert": {
         "version": "1.4.0"
     },
+    "webmozart/glob": {
+        "version": "4.1.0"
+    },
+    "webmozart/path-util": {
+        "version": "2.3.0"
+    },
     "zendframework/zend-code": {
         "version": "3.3.1"
     },