Add a maxRestartCount option

Allowing us to control the maximum clangd restart times (by default it is 4), this
would make the life of tracking/reporting crashes a bit easier.

package.json

@@ -124,6 +124,11 @@
                     "default": true,
                     "description": "Always rank completion items on the server as you type. This produces more accurate results at the cost of higher latency than client-side filtering."
                 },
+                "clangd.maxRestartCount": {
+                    "type": "number",
+                    "default": 4,
+                    "description": "The maximum count that the extension will restart clangd if clangd crashes."
+                },
                 "clangd.checkUpdates": {
                     "type": "boolean",
                     "default": false,

src/clangd-context.ts

@@ -129,6 +129,9 @@ export class ClangdContext implements vscode.Disposable {
 
     this.client = new ClangdLanguageClient('Clang Language Server',
                                            serverOptions, clientOptions);
+    this.client.clientOptions.errorHandler =
+        this.client.createDefaultErrorHandler(
+            config.get<number>('maxRestartCount'));
     if (config.get<boolean>('semanticHighlighting'))
       semanticHighlighting.activate(this);
     this.client.registerFeature(new EnableEditsNearCursorFeature);