Disable-auto-language-update

[tapple]

• Adds a setting to disable the plugin from updating the language definitions for luau-lsp and selene automatically
• Change Force Language Update to work even when not connected to a viewer

I'm using the updated language files from the lsl-definitions repository, and the plugin keeps trying to downgrade them. I can usually revert the changes it made and reload the Luau language server, but this doesn't always work. sometimes problems luau-lsp found when using out-of-date defs don't go away on reload, and I have to restart vscode to get rid of them. But then restarting vscode would cause sl-vscode-plugin to mess up the definitions again

[Rider-Linden]

Sorry this took me so long to look at. Just one minor change.