Support for other git based version control tools

[joshuakto]

I think the best way to add support for other git-based version control tools (e.g., gitea, gitlab, etc.) would be to enable the initialization of the plugin with different fit classes. Each fit class would support a specific git tool (e.g. gitlab), and implement the IFit interface so it will work nicely with the plugin. This way, anyone in the community who would like to contribute to this plugin with a new tool support would be able to do so. https://github.com/joshuakto/fit/blob/8878193d48d866a05dcd78f1599f4af068c69c5b/src/fit.ts#L9 If someone thinks of a better approach, please feel free to suggest them!