[vscode][5/n] Setup Env Variables: Read the text from the env templat…

…e and append to existing file

TSIA, and making the function async now that we call an await statement


## Test Plan

vscode-extension/src/extension.ts

@@ -58,8 +58,8 @@ export function activate(context: vscode.ExtensionContext) {
   context.subscriptions.push(
     vscode.commands.registerCommand(
       COMMANDS.SETUP_ENVIRONMENT_VARIABLES,
-      () => {
-        setupEnvironmentVariables(context);
+      async () => {
+        await setupEnvironmentVariables(context);
       }
     )
   );
@@ -764,13 +764,9 @@ async function setupEnvironmentVariables(context: vscode.ExtensionContext) {
   );
 
   if (fs.existsSync(envPath)) {
-    var helperText: string = "\ntest, will change next PR";
-    // fs.readFile(envTemplatePath.fsPath, function read(err, data) {
-    //   if (err) {
-    //     throw err;
-    //   }
-    //   helperText = "\n" + data.toString();
-    // });
+    const helperText = (
+      await vscode.workspace.fs.readFile(envTemplatePath)
+    ).toString();
 
     // TODO: Check if we already appended the template text to existing .env
     // file before. If we did, don't do it again