lines, barebones drawing window

addition of lines means ipc slightly changed, though can be ignored. also, minor malvim fix

docs/window-likes/draw.md

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+Very basic drawing board.
+
+## Moving
+
+Arrow keys or hjkl. `i` to enter input mode. Use the enter key to finish a line or rectangle. Escape to cancel line or rectangle in progress.
+
+## Input Commands
+
+- `line`: Start line with current point as start. Move and hit enter to determine line endpoint
+- `rect`: Start rect with current point as a corner. Move and hit enter to determine the opposite corner
+- `color/c/colour [lowercase 6 char hex string]`: Set current colour
+- `linewidth/lw [int]`: Set current line width
+- `undo`: Undo last draw
+- `clear`: Clear all drawings