Tweak the Loogle search implementation slightly in a few ways.

[Julian]

• Fix Loogle sometimes returning responses with newlines, breaking nvim_buf_set_lines which wants none -- e.g. Complex.cos_add_mul_I returns a type with newlines in it. What we do now is split, then indent any newlines so the preview file looks "reasonableish"
• Make the result be put charwise, so that e.g. #check will never insert extra lines
• Make it usable outside of telescope via require'lean.loogle'.search(), which simply returns results
• Add some more typing for Loogle API responses
• Use Lua errors (exceptions) in a place or two to avoid some manual error checking

There's probably a few small other things that can be tidied.

[Julian]

These are all quite minor I think, and mostly was a way to just poke at your code. Will give it a fresh look in the morning before merging, but @hargoniX if you have any comments feel free to lemme know!

[Julian]

I meant to check if Loogle ever returns names with newlines for any absurdly long one. Hopefully not but leaving a just in case note to check.

[hargoniX]

No I don't think it should do that but @nomeata should probably know the details on that? I'm a little surprised about the types with newlines as well, can you comment on that Joachim?

Apart from that I believe the changes look fine.

[nomeata]

I'm using some delaborator that I found, but plan to refine that anyways (more concise syntax where possible, maybe omitting some types or names…), I can try to avoid newlines then. but better be defensive - s/\n/ / doesn't hurt

[Julian]

Thanks both!