feat: add testing infrastructure

Author: olafurpg

.gitignore

@@ -3,3 +3,4 @@ node_modules
 *.vsix
 coverage/
 .nyc_output/
+.vscode-test

.vscode/launch.json

@@ -18,7 +18,7 @@
       "type": "extensionHost",
       "request": "launch",
       "runtimeExecutable": "${execPath}",
-      "args": ["--extensionDevelopmentPath=${workspaceRoot}", "--extensionTestsPath=${workspaceRoot}/out/test"],
+      "args": ["--extensionDevelopmentPath=${workspaceRoot}", "--extensionTestsPath=${workspaceRoot}/out/test/suite/index"],
       "stopOnEntry": false,
       "sourceMaps": true,
       "outFiles": ["${workspaceRoot}/out/test/**/*.js"],