New Commands for VIM Interop

[altnp]

Is your feature request related to a problem? Please describe.
As an extension developer, I would like to support VIM users better by being able to detect their current mode and change it when they take certain actions.

Describe the solution you'd like
Two new commands:

vim.getMode returns the current VIM mode
vim.setMode changes the current mode to a valid VIM mode

Describe alternatives you've considered
I tried getting the current mode from context but the VS Code API does not allow this.
Additionally, I tried sending keys using the type command to the editor, which works, but is inconsistent if the user has done any re-maps.