marks on double click selection using firefox fix

[tdaron]

Description

This PR contains a quick-fix of marks function using Firefox. This was already fixed, but the fix was removed inside of #5486. I put it back but this time only in marks code instead of selection handling one, so it should not affect anything else.

Issue
Fixes: #5574 #5560

Example
Before the fix:

When fixed:

Context

This is related to firefox weird selection range when double clicking.
Explanation from original fix:
* suppose we have this document:
*
* { type: 'paragraph',
* children: [
* { text: 'foo ' },
* { text: 'bar' },
* { text: ' baz' }
* ]
* }
*
* a double click on "bar" on chrome will create this range:
*
* anchor -> [0,1] offset 0
* focus -> [0,1] offset 3
*
* while on firefox will create this range:
*
* anchor -> [0,0] offset 4
* focus -> [0,2] offset 0

Checks

• The new code matches the existing patterns and styles.
• The tests pass with yarn test.
• The linter passes with yarn lint. (Fix errors with yarn fix.)
• The relevant examples still work. (Run examples with yarn start.)
• You've added a changeset if changing functionality. (Add one with yarn changeset add.)

[changeset-bot]

🦋 Changeset detected

Latest commit: a58c546

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
slate	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[12joan]

Nice! Can you add a unit test for the case that affects Firefox, and add a changeset?

[tdaron]

Nice! Can you add a unit test for the case that affects Firfox, and add a changeset?

I tried to add one, i hope i did it the right way :D

[12joan]

I think this change should be a patch rather than a minor, since it's a bug fix. Minor usually means non-breaking feature changes.

[12joan]

Thanks for making those changes. Did you want to add a unit test?

[tdaron]

Thanks for making those changes. Did you want to add a unit test?

IDK how to make them the right way..

[12joan]

If you grant me commit access to your fork, I can add one later today. 🙂

[tdaron]

If you grant me commit access to your fork, I can add one later today. 🙂

done !

[12joan]

Thanks. I've added the test.

[12joan]

The integrations test failures are unrelated to this PR and can be safely ignored

[bradcypert]

Wow, awesome! Thank you for working on a fix for my issue. I had really wanted to use Slate but this was a blocker for me, so I started exploring alternatives -- now I can go back to slate! :D