Changes built output to be gitlens.js

Helps avoid source map conflicts with other extensions

package.json

@@ -20,7 +20,7 @@
 	"engines": {
 		"vscode": "^1.45.1"
 	},
-	"main": "./dist/extension",
+	"main": "./dist/gitlens",
 	"icon": "images/gitlens-icon.png",
 	"preview": false,
 	"badges": [

webpack.config.js

@@ -139,7 +139,7 @@ function getExtensionConfig(mode, env) {
 		devtool: 'source-map',
 		output: {
 			libraryTarget: 'commonjs2',
-			filename: 'extension.js',
+			filename: 'gitlens.js',
 			chunkFilename: 'feature-[name].js',
 		},
 		optimization: {