Don't close sticker picker if shift is pressed when sending stickers

[hackerbirds]

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Description

On the mobile apps, the sticker picker stays open when we send stickers, until we decide to close it. This is useful if you want to send multiple stickers quickly. But on Desktop, the interface has to be different, and currently the sticker picker automatically closes right after sending a sticker. This is nice, but if we want to send multiple stickers quickly, we need to reopen the sticker picker, find the sticker pack we want, resend sticker etc.

This PR adds the ability to prevent the sticker picker from closing when we send a sticker if the shift key is held down.

Things to mention:

• It also affects the sticker picker in the media editor though I don't see this as an issue I feel that it should be pointed out
• Since there was already a shortcut making use of shift I simplified the code by "merging" the shiftHeld state with the previous shortcut code to prevent having two separate events handling shift.
• The recent stickers would update below your eyes if you send recent stickers with the tab still open, so I put them behind a state that only updates when the sticker picker is opened. I have still lots to learn with React so let me know if this is the right thing to do.

[hackerbirds]

Dunno if that's necessary but I rebased/updated my branch.

[hackerbirds]

Hi, the PR is now rebased for v6.29.0.beta-1. It was also tested again to make sure it is still working properly. Lmk if there's anything that should be changed.

[jamiebuilds-signal]

Thank you for this PR, apologies for it taking this long to get reviewed

[hackerbirds]

Thank you for this PR, apologies for it taking this long to get reviewed

No worries, I know how busy y'all have been recently.

I made the following changes using your feedback, let me know if these are okay:

• I moved the "close on sticker pick" event inside StickerPicker's onClick which is where the event.shiftKey check is done.
• To prevent re-rendering recent stickers, I changed the recentStickers state that was inside StickerButton and used a useRef inside StickerPicker. There is a side effect to that though: if a user sends recent stickers, then switches from the recent stickers tab to another tab, and then switches back to the recent stickers tab, nothing will have updated, because now recentStickers will only update after the sticker picker is completely closed. I don't think it's worth worrying about, but it should be pointed out still.

[hackerbirds]

Hey, is this PR still of interest? Should I rebase it, modify something, or just close the PR?