feat(harper-core): Mark shebangs as unlintable

[sohunpatel]

Closes #65.

Changes

• Adds check to see if the content is a shebang, in the parse function.
• Add test to comment parser to make sure that comments with shebang are ignored

I am not sure if this is a great solution since this should only apply to comment parsers, but I could not find an elegant solution for that.

[grantlemons]

I think a better solution would be to mask them out in harper-tree-sitter. See fd5ebae.

[elijah-potter]

@grantlemons, @sohunpatel I think the best way to do this would be to create a new implementaion of the Masker trait that ignores lines with shebangs. From there, it'd wrap it around the inner Masker that CommentParser uses internally.

Let me know if you have any questions about any of that.