[Shape-builder]: enable ESC and Double Click to close shape

[parthivsaikia]

Notes for Reviewers

• This PR fixes Add esc and double tab feature to exit shape builder #72
• Related to PR Added the better way to see the instructions #73 (Includes the UI updates to display the new ESC shortcut)

Signed commits

• Yes, I signed my commits.

Description

This PR implements standard "exit" behaviors for the Shape Builder tool to match common UX patterns.

Changes:

1. Logic (ShapeBuilder.js):

   • Added event listener for Escape key to close the shape.
   • Added onDoubleClick event to the drawing canvas to close the shape.
   • Refactored the "Close Shape" logic into a reusable finishShape function.

2. UI (index.js):

   • Updated the instructions bar to explicitly list ENTER / ESC as valid closing keys.
   • (Note: Applies the "Keyboard Style" UI updates to ensure the ESC key is displayed clearly).

Testing

• Tested Escape key while drawing -> Closes and fills shape.
• Tested Double Click on grid -> Closes and fills shape.
• Verified Enter key still works as expected.

Screenshots

[saurabhraghuvanshii]

thanks @parthivsaikia lgtm