Implement the Dimensions effect for xterm.js.

[LSUDOKO]

Fixes #24: Implement Dimensions effect for xterm.js

This commit implements the Dimensions effect for the xterm.js backend, enabling users to get the terminal's columns and rows, and to resize the terminal.

Key Changes:

1. core/js/src/main/scala/terminus/XtermJsTerminal.scala:

   • Added the necessary facade methods to interact with xterm.js's dimension properties and resize functionality:
     • def cols: Int
     • def rows: Int
     • def resize(cols: Int, rows: Int): Unit

2. core/js/src/main/scala/terminus/XtermJsOptions.scala:

   • Modified the apply method to ensure a consistent parameter order for dimensions: cols: Int = 80, rows: Int = 24.

3. core/js/src/main/scala/terminus/Terminal.scala:

   • The Terminal class now extends the effect.Dimensions trait.
   • Implemented getDimensions to retrieve the current terminal dimensions (TerminalDimensions(terminal.cols, terminal.rows)).
   • Implemented setDimensions to resize the terminal using terminal.resize(dimensions.columns, dimensions.rows).
   • Added a dimensions helper object within the Terminal companion object for a cleaner API (e.g., Terminal.dimensions.get).
   • Updated the run method (that accepts id, cols, rows) to call XtermJsOptions with the cols parameter first, then rows, maintaining consistency.

These changes provide the core functionality requested in issue #24 for the xterm.js environment. The coreJS/test suite passes with these modifications.

[noelwelsh]

Looks good apart from one change.

[noelwelsh]

I think this should extend Dimensions

[noelwelsh]

Thanks!