Change drag events in the map editor into pointer down events

[white-axe]

Connections

• Closes [BUG] Clicking on tiles in the map view or tilepicker doesn't select/edit tiles #117

Description
This pull request changes the trigger for drawing tiles on the map and for selecting tiles in the tilepicker from dragging the mouse to just having the primary mouse button down. This allows tiles to be drawn/selected immediately when the primary mouse button is down instead of requiring the user to move the mouse slightly.

Testing
It should no longer be required to drag the mouse slightly for tile drawing/selection to be triggered, although they should still trigger when dragging the mouse. In addition, they should still only trigger when the primary mouse button is down rather than any mouse button.

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown -Z build-std=std,panic_abort
• Run cargo build --release
• If applicable, run trunk build --release