Viability of mobile (Android) build

[pacjo]

Pixelorama version: v1.0 (855f72a)

OS/device including version: Android tablet (Mi Pad 6), LineageOS 21

Issue description:

I saw there's no official support for mobile builds, at first I thought it was caused by godot 3, but after update to 1.0 (congrats by the way) and switch to godot 4, I decided to give it a try.

When opening the project for the first time a bunch of resource related errors appear (but the same happens on desktop, so probably nothing important). Running it regardless of the popups works fine.

Stylus (Xiaomi Smart Pen 2 in my case) works out of the box (even with hover support). Nothing crashes, most things look right (aside from smaller screen then on desktop).

Of the issues I noticed, it looks like some fonts are pixelated (mainly in the menus, maybe #1065 related?), I also couldn't find a way to switch to the right tool, there's some wierd graphical issues along pixel edges on the canvas and Pixelorama complains about missing some .json palette file. Palm rejection could use some work too, but that's a minor thing.

Also undo / redo (as well as other shortcuts) are... hard to use without a keyboard, but this could probably be fixed with a custom toolbar showing a couple of user defined buttons. (I'd like to add this, can you point me to the relevant part of the code?)

Also I feel like it's important to say, that I use only basic functionality of the app, so I wasn't able to test more advanced features.

Steps to reproduce:

1. Import project into Godot
2. Select Edit to see the above mentioned errors
3. Select Run to successfully run the app

EDIT(s):

• It seems like Manage External Storage permission is required for opening .pxo files from internal storage
• Also writing in some text fileds is impossible as it removes previous text and hides keyboard after the first character (visible when renaming layer). Not all text fields are affected - renaming file in the Export as dialog works as expected
• I didn't find a way to select multiple things (like when selecting frames in the animation menu)
• repositioning canvas with two fingers is broken (could probably be easily fixed with scrollbars for vertical and horizontal movement) and there's no zooming with a pinch gesture

[pacjo]

Uhh, this probably should be in discussions instead of being a bug report, can you move this? Sorry.