Add a option to desactivate <<= and >>= ligatures

[GrayJack]

Some languages uses <<= and >>= as bitshift assign operators, like Rust and Zig, and the ligatures look weird in those contexts, so I propose creating a new stylistic set that deactivate the ligatures for those or change the ligatures to better represent bitshift assign operators.

What are your thoughts?

[tonsky]

I’m not agains, but there is a limited amount of stylistic sets. I’ll see how it aligns with the others. Thanks!

[Seltyk]

If this gets implemented I would argue the stylistic set would change how >>=, >>>=, and <<= only are rendered. They deserve ligatures, and the usual arrow behavior is lovely, but I can see why those three in particular look a bit… bleugh in bitwise code as arrows. If that makes sense