Enhancement request to have API to add debugger type

[pchuong]

The RTOS view already allow the user to add additional debugger type using settings window. I like to request to have an API to allow other extension to add additional debugger type programmatically.

I made the change locally and tested with my debugger type, I can create a PR for this change.

[haneefdm]

Go ahead and create a PR. It can also be a vscode command rather than an API returned by the activate function

[pchuong]

Here is the PR #101.