Add Jump to Tile Coordinates feature

[sirajahmadzai]

This PR implements the "Jump to location by tile coordinates" feature requested in issue #1367.

Changes:

• Add TileLocatorSource for parsing tile coordinates
• Add "Jump to Tile" action with Ctrl+Shift+G shortcut
• Support multiple coordinate formats: x,y, x:10 y:20, 10 20, etc.
• Update keyboard shortcuts documentation

Testing:

• Created test applications to verify coordinate parsing
• All supported formats work correctly
• Invalid inputs are properly rejected

Files Changed:

• src/tiled/tilelocator.h - New header file
• src/tiled/tilelocator.cpp - New implementation
• src/tiled/mainwindow.ui - Added action and menu item
• src/tiled/mainwindow.h - Added method declaration
• src/tiled/mainwindow.cpp - Added method implementation
• src/tiled/libtilededitor.qbs - Added to build system
• docs/manual/keyboard-shortcuts.rst - Updated documentation

Fixes #1367