fix: image inline resizable issue

[semanticist21]

Fix issue related with #211

I moved 'mousdown' state value to the parent and improved selected logic.
I added some comment on the code.

Tested on with both option inline true and false, and it worked fine for me.

[semanticist21]

@sjdemartini
May you look up or review this pull request to be merged?
I am currently using mui-tiptap by editing codes by myself due to this bug.
I hope to use it in an offical version soon.

[sjdemartini]

@semanticist21 Thanks for investigating a fix and making the PR. I'll plan on looking at this and testing it out soon and will get back to you.

[semanticist21]

Thank you.
Give me any feedback to fix if needed!

[semanticist21]

restored branch

[semanticist21]

restored mistakenly deleted branch.

[sjdemartini]

Thanks again @semanticist21! Good find and clever solution. It's a bit odd to me that Tiptap removes the selected state of the node when dragging the resize handle only when inline: true, but this does seem to work for both inline: true and inline: false and seems like a reasonable solution to me!