docs: add minimum VS Code engine to troubleshooting guide

Fixes golang/vscode-go#1588

Change-Id: Ic3ff5e64005e278a2a1342fcb003e4ee5b70e42c
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/331410
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 908a158..e28abcb 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -69,7 +69,7 @@
 
 1. Your Go version: `go version`
 1. Your `gopls` version: `gopls -v version`
-1. Your vscode version: `code -v`
+1. Your vscode version: `code -v` (The minimum required VS Code version is in the ["engines"](https://github.com/golang/vscode-go/blob/master/package.json#L89) attribute in the package.json file.)
 1. Your Go extension version: `Extensions: Show Installed Extensions`
 1. Your Go environment: `go env` in the workspace folder
 1. Relevant VS Code settings: run `Preferences: Open Settings (JSON)` and include anything in a `[go]` block, and anything that starts with `go.` or `gopls.`