Fix display for other file types besides Elm modules

The previous implementation only considered Elm modules in the setup of the Monaco editor and surroundings, resulting in suboptimal visuals.
The changes in this commit expand support to other file types, specifically JSON, XML, Markdown, HTML, and CSS.
Also, display the 'Format' and 'Compile' buttons only when these are usable on the file currently open in the editor.

implement/example-apps/elm-editor/src/Frontend/FileEditor.elm

@@ -0,0 +1,40 @@
+module Frontend.FileEditor exposing (..)
+
+
+type FileContentType
+    = ElmContent
+    | JsonContent
+    | XmlContent
+    | MarkdownContent
+    | HtmlContent
+    | CssContent
+
+
+fileContentTypeFromFileName : String -> Maybe FileContentType
+fileContentTypeFromFileName fileName =
+    case fileName |> String.split "." |> List.reverse of
+        [] ->
+            Nothing
+
+        fileExtension :: _ ->
+            case String.toLower fileExtension of
+                "elm" ->
+                    Just ElmContent
+
+                "json" ->
+                    Just JsonContent
+
+                "xml" ->
+                    Just XmlContent
+
+                "md" ->
+                    Just MarkdownContent
+
+                "html" ->
+                    Just HtmlContent
+
+                "css" ->
+                    Just CssContent
+
+                _ ->
+                    Nothing