I’m not sure that the ligatures for dotted operators are such a great idea, though. For example, how would .⋅ appear if you defined a ligature similar to the one you have for .-? The raised dot in your ligature looks an awful lot like a multiplication operator.
Note also that <<= is an assignment operator in Julia and many other languages, and the current ligature doesn’t reflect this (https://github.com/tonsky/FiraCode/issues/560).
The other problem I have when looking at some of these ligatures is that if I’m looking at someone’s code and see a non-obvious ligature, I might not know how to type it. My first guess would be that it is some Unicode character (Julia supports a lot of those and they are common in Julia code), not a ligature.
Note also that -> => ⟶ ⟹ are all distinct operators in Julia. It seems that your ligatures make the first two look very similar to the latter two, which is a problem. (Filed https://github.com/tonsky/FiraCode/issues/559) This illustrates the general danger of mixing fancy ligatures with a language that supports both ASCII and Unicode operators.