Auto-completion with a package prefix

[jalaziz]

I'm not sure if this is an LSP issue or an extension issue, but auto-completion doesn't work for package prefixes.

For example, if I have a protobuf message at foo.v1.Bar, typing foo. doesn't present the v1 package. Subsequently, typing foo.v1., doesn't present the Bar option.

However, if I type B.., Bar will show up as an option and will auto-complete to the full path when you hit <TAB>.