Dafny project file improvements (#475)

### Changes
- No longer let the syntax definitions for .dfy files also be applied to
dfyconfig.toml files
- Activate extension when `.toml` file is opened, such as a
`dfyconfig.toml`
- Let the language client also operate on files ending in
`dfyconfig.toml`

### Testing
- Manually tested that only opening a `dfyconfig.toml` will already
trigger the extension and provide diagnostics.
- Manually tested that making changing in a `dfyconfig.toml` file causes
diagnostics to be updated
- Manually tested that syntax highlighting for `dfyconfig.toml` files
works correctly.

Author: keyboardDrummer

language-configuration.json dafny-language-configuration.json

@@ -11,6 +11,9 @@
   "bugs": {
     "url": "https://github.com/dafny-lang/ide-vscode/issues"
   },
+  "activationEvents": [
+    "onLanguage:toml"
+  ],
   "qna": false,
   "license": "MIT",
   "galleryBanner": {
@@ -123,10 +126,9 @@
         ],
         "extensions": [
           ".dfy",
-          ".dfyi",
-          "dfyconfig.toml"
+          ".dfyi"
         ],
-        "configuration": "./language-configuration.json"
+        "configuration": "./dafny-language-configuration.json"
       }
     ],
     "grammars": [
@@ -309,7 +311,6 @@
       }
     ]
   },
-  "activationEvents": [],
   "scripts": {
     "vscode:prepublish": "npm run package",
     "compile": "webpack",

package.json

@@ -152,7 +152,11 @@ export class DafnyLanguageClient extends LanguageClient {
     };
     const diagnosticsListeners: ((uri: Uri, diagnostics: Diagnostic[]) => void)[] = [];
     const clientOptions: LanguageClientOptions = {
-      documentSelector: [ DafnyDocumentFilter ],
+      documentSelector: [ DafnyDocumentFilter, {
+        scheme: 'file',
+        pattern: '**/*dfyconfig.toml'
+      }
+      ],
       diagnosticCollectionName: LanguageServerId,
       middleware: {
         handleDiagnostics: (uri: Uri, diagnostics: Diagnostic[], next: HandleDiagnosticsSignature) => {