Use prettier organize imports plugin

Also remove unused dev dependencies from **/package.json

packages/adl-language/package.json

@@ -24,8 +24,6 @@
     "@types/mkdirp": "~1.0.1",
     "@types/node": "~14.0.27",
     "ecmarkup": "~7.0.3",
-    "prettier": "~2.2.1",
-    "typescript": "~4.2.4",
     "watch": "~1.0.2"
   }
 }

packages/adl-rest/package.json

@@ -35,7 +35,6 @@
   },
   "devDependencies": {
     "@types/node": "~14.0.27",
-    "prettier": "~2.2.1",
     "typescript": "~4.2.4"
   }
 }

packages/adl/package.json

@@ -56,6 +56,7 @@
     "grammarkdown": "~3.1.2",
     "mocha": "~8.3.2",
     "prettier": "~2.2.1",
+    "prettier-plugin-organize-imports": "~1.1.1",
     "source-map-support": "~0.5.19",
     "typescript": "~4.2.4"
   }