Handle mobile touch gestures for scene controls

[syzer]

It's mostly JS for handling touch gestures on canvas.
Rust change is tiny.
As always contains previous PR's

WARNING NEED TEST ON NATIVE IPHONE... for android the axis were inverted than web version .. as example

• Add mobile touch gesture handling in web bootstrap (index.js): one-finger rotate, two-finger pan + pinch.
• Add touch gesture bridge in WASM core and apply deltas in camera controls.
• Lock page-level zoom/pan gestures so touch interaction stays inside the canvas.
• Update startup hint text to include mobile controls.
• Fix Android/Chrome pinch direction in camera scaling (sign normalization).

[unkcpz]

Do you think it can or it should to have this also in rust through web-sys (or gloo)? That is what we did for the original drag and drop.

If you don't mind, I'll give it a try after merge this PR.

[unkcpz]

Okay, I see. If I understand it corretly, you collect the gestures by js and then send a payload to the rust side.

[syzer]

yes

[syzer]

i like your idea: but try to run it locally on your phone first to see if experience is good...

[syzer]

theres a big PR on top of it.. but maybe we can rebase that on top of oyur changes :D

[unkcpz]

I gave it a try and works well (on my iphone, with firefox). Only problem is when touch an atom it is not selected.

For the javascript part, you may notice that there is another index.js in wasm/ folder. I use that one for the github page deployment. There are only slightly different, the deployed one take care of the loader when wasm is initializing.

I think we can move the mobile gesture into a dedicated js file and load both, I'll give it a try and commit directly here.

[unkcpz]

Okay, I decide to keep the javascript part. It is a good example to show that there are two ways to communicate between bevy world and web api world.
I add a commit to separate the mobile gesture logic out, so if can be used in github page deployment, which copy another index.js from wasm/ folder.