Hint about gopls multi-module workspace support

[ottob]

Describe the bug
Not really a bug but a hint for other go users.

To Reproduce
Steps to reproduce the behavior:

1. have a single git repo with many go modules.
2. try to use lsp features like goto definition.
3. fail with errors like no object found for ident X

Expected behavior
LSP features to work.

Additional context
In gopls v0.5.3 an experimental mode for multi modules was added. I enabled it in my sublime lsp config like this:

"gopls":
	{
		"enabled": true,
		"initializationOptions": {
			"experimentalWorkspaceModule": true
		}
	},

Then goto definition etc works as expected.

[rwols]

If you are feeling adventurous, consider updating docs/index.md in this repository with your knowledge, and make a pull request.

[rwols]

Fixed by #1490