Support downloading databases from LGTM.com using just the project slug

[tausbn]

Is your feature request related to a problem? Please describe.
When specifying a database on LGTM.com to download, one has to specify the entire URL for the corresponding project, even though the project slug should be sufficient. In much of our tooling, projects are identified using just the slug, and so it's more difficult to quickly import a database of interest than it perhaps ought to be.

Describe the solution you'd like
Ideally, the extension would recognise strings that match LGTM.com slugs (e.g. g/github/codeql or b/bitbucket/whatever) and automatically add the https://lgtm.com/projects/ prefix.

Describe alternatives you've considered
My current alternative is to manually type in the prefix. This gets old fast.

Additional context
None.

[aeisenberg]

Yep. This makes sense. The original implementation assumed users would copy/paste from the browser's url bar. It shouldn't be hard to implement a different way of specifying the database name.