Add minimum iOS version to HTML export

**Your Godot version:**
4.7.1

**Issue description:**
I have exported a small game for the web using the HTML5 export in project settings. Nothing fancy mostly all standard. On Android and PC no problem to load the game, but on iOS 15 it stuck on the loading screen. To debug this and see what is going on I installed 'eruda' to see the console and there a strange error popped up:
```
CompileError: WebAssembly.Module doesn't parse at byte 88: invalid opcode 253, in function at index 231
```
and after a reload of the page and starting the game:
```
CompileError: WebAssembly.Module doesn't parse at byte 5: can't get Function local's type in group 1, in function at index 0
```
After some more digging and back-and-forth with an LLM is seems iOS 15 does not support SIMD which is used in the export. Only iOS version 16 and higher supports SIMD.

So IMO it would be a good idea to put a remark in the documentation to let others know that only iOS 16+ is supported.

Or is this a bug because Godot wants to support iOS 15?

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/tutorials/export/exporting_for_web.html

Start with the web export documentation page linked in the issue and review its existing platform requirements. Verify the iOS 15 SIMD limitation and whether iOS 16 is the supported minimum, then add a clear compatibility note; the work is done when the page accurately states the minimum iOS version for HTML exports.

Written by the indexing model from the issue text.