Add two-finger pan to move the text in all directions

[dronov-dmitry]

Summary

Adds a two-finger pan gesture: while two fingers are pressed on the text, dragging moves the text in any direction (left/right/up/down).

How it works

• New TwoFingerPanTouchListener attached to the editor EditText in EditorActivity.
• When a second pointer goes down, the listener takes over the gesture and scrolls the content to follow the fingers (focal point of the two pointers).
• Works in both layouts:
  • default (ScrollView) — vertical scroll via the ScrollView, horizontal via the EditText;
  • "simple scrolling" — both axes via the EditText.
• Scrolling is clamped to the content bounds (panContent/clampScroll) so the text cannot be panned past its edges.
• Single-finger behavior (cursor placement, selection, drag scrolling) is untouched.

Note: horizontal panning only applies when text is wider than the screen, i.e. when auto-wrap is turned off.

Verification

• ./gradlew compileDebugJavaWithJavac — OK
• ./gradlew testDebugUnitTest — OK
• ./gradlew lint — no errors

Video

https://youtube.com/shorts/mreTjptc4fY

[maxistar]

Thanks for this contribution! The implementation looks good and the CI passes. We identified a few edge cases that we can cover with tests and refine separately, but they are not blockers for merging. Great work!