Add integration test for buildifier (#15)

* Add integration test for buildifier
* Revamp downloader
* Declare user-agent and maybe use auth token
* Allow override env var for rate limits
* Make GITHUB_TOKEN env var visible to step
* Fix buildifier test on windows

Author: pcj

.github/workflows/ci.yaml

@@ -21,5 +21,7 @@ jobs:
         run: npm install
       - name: Run headless test
         uses: GabrielBB/xvfb-action@v1.0
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           run: npm test

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+	// See http://go.microsoft.com/fwlink/?LinkId=827846
+	// for the documentation about the extensions.json format
+	"recommendations": [
+		"dbaeumer.vscode-eslint"
+	]
+}

README.md

@@ -86,4 +86,7 @@ None currently.
 
 ## Known Issues
 
-N/A
+**Github Rate Limits**: This extension makes requests to the github v3 API.  If
+you experience errors due to rate limits, `export
+GITHUB_TOKEN={MY_PERSONAL_TOKEN}` and relaunch vscode  to get higher rate
+limits.