Add swift as a supported language to analyze

[ericwb]

Is your feature request related to a problem? Please describe.
Swift is a language that might not have much coverage by other SAST tools, so would be nice to have an advantage there.

Describe the solution you'd like
Utilize the tree-sitter-swift package to do analysis. Unfortunately, currently it does not reside on PyPI, thus making install of the precli package worse. Maybe later when it does get incorporated into PyPI, this feature can be implemented fully.

Describe alternatives you've considered
n/a

Additional context
https://github.com/alex-pinkus/tree-sitter-swift

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