Add a button to switch between fixed and floating joystick modes

[viatearz]

Summary

Some games only support floating joystick (also called dynamic joystick or free joystick), but PlayTools currently defaults to a fixed joystick, causing it to not work properly in certain games.
Although increasing the size of joystick element in the keymapping editor can make it work, many users don't know this workaround.

Explanation

File	Changes
Elements.swift	Added a mode field in struct Joystick, use Optional type to ensure compatibility with older keymapping configuration files.
PlayAction.swift	Simulate touches for both fixed and floating joystick modes.
EditorController.swift Joystick.swift JoystickElement.swift	Added a button UI in the mapping editor to switch joystick modes. To prevent accidental clicks, the button only appears when the joystick element is focused.
PlayTools.strings	Added keys keymappingEditor.joystickMode.fixed and keymappingEditor.joystickMode.floating.

Screenshot

Related Links

• Game Link: 燕云十六声
• Possibly related issue: [Bug]: joystick thingy drift left everytime i press wasd,(with keymapping) pls help me how to fix it PlayCover#1794

[TheMoonThatRises]

Since this change updates the structure of keymappings, can you also make a PR that reflects the changes in the PlayCover app too? If not, thats fine, I can do it.

[viatearz]

Since this change updates the structure of keymappings, can you also make a PR that reflects the changes in the PlayCover app too? If not, thats fine, I can do it.

Alright, I have done it. Please take a look.

[XuYicong]

Good job! I'm concerned of the keymap compatibility tho. People may open an old keymap with the new software, or open a new keymap with an old software. I'm not sure if that could cause problems, but if you think that's not a big case then I'll just let it be.

[TheMoonThatRises]

I think keymap compatibility is outside the scope of this PR, as PlayTools usually relies on PlayCover to update the keymap format. But a later PR can be created so that PlayTools has a proper decoder similar to how PlayCover does it.