pebble-sdk: install docs to doc folder

Closes #29065.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
pebble-sdk 2.1.1

Closes #29402.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
pebble-sdk: update 2.1.1 bottle.
gtk+3: update 3.12.2 bottle.