Support inline errors

Intellij's Bazel plugin supports showing errors inline. It's unclear if this is possible using Bazel's VS Code plugin. I don't see an obvious way to enable this.

Start by comparing the inline-error behavior described for IntelliJ's Bazel plugin with the capabilities documented for the Bazel VS Code plugin. Determine whether VS Code can support this and identify the plugin entry points or diagnostics documentation that apply. Done means either documenting how to enable inline errors or defining the implementation scope if they are not currently supported.

Written by the indexing model from the issue text.