Support double and triple click for highlighting text

[CosmicHorrorDev]

Currently text highlighting only works by dragging a selection. It would be nice to support double and triple click to handle selecting the hovered word and line respectively

[trimental]

This would be a nice feature. The only thing is that wgpu glyph controls the layout of text almost entirely. It has its own rules on when to make a new line etc, so the triple click might be harder to implement.

I suppose for the double click it'll be a case of searching forwards and backwards from the closest glyph to the cursor for whitespace characters and selecting in-between.