Add the command in the issue template

Author: akshita31

ISSUE_TEMPLATE

@@ -1,4 +1,10 @@
-Please prefer filing issues through the in-built extension command `CSharp: Start authoring a new issue on GitHub`. Know more - https://github.com/OmniSharp/omnisharp-vscode/wiki/Reporting-Issues.
+<!-- To prefill this information:
+1. Open Visual Studio Code
+2. Bring up the command palette (press <kbd>F1</kbd>)
+3. Type `CSharp: Report an issue`
+
+If the `CSharp: Report an issue` command doesn't appear, make sure that you have C# extension version 1.17.0 or newer installed.
+-->
 
 ## Environment data
 `dotnet --info` output: