Android fix (Gboard)

[omega1996]

fixes #40 and #170

I've taken the code snippet from #40 (comment).
thank to equilerex
hpierre74 also asked for this fix #40 (comment)

[simboel]

@csculley can you please have a look at this?
I'm also affected by the problem that PR tries to fix.

[csculley]

Sorry for the delay, but this PR looks to be our best and most minimal option at mitigating the issue without waiting for a fix to come from upstream in Quill or ideally Android...
I can't see Android keeping this behavior long term, it's so problematic, but who knows since the earliest report I've seen is from 2014....
wxik/react-native-rich-editor#208 (comment) contains even more references to this problem 😭

[simboel]

@csculley I've implemented the fix in my application and found that there are some edge cases. I will validate this and provide an updated version of this PR.

One problem is for example that changes to attributes (i.e. data- attributes) will simply delete the mention blot completely.
But I fixed these and need a little bit more time to prepare the fix.