Would it be possible to implement background blurring in sway?

In X11, compositors like compton can efficiently apply arbitrary convolution kernels specified in their config files. Here's an example of such a kernel (5x5 gaussian):

5,5,0.018316,0.082085,0.135335,0.082085,0.018316,0.082085,0.367879,0.606531,0.367879,0.082085,0.135335,0.606531,0.606531,0.135335,0.082085,0.367879,0.606531,0.367879,0.082085,0.018316,0.082085,0.135335,0.082085,0.018316,

It would be nice to have something similar in sway, especially since the implementation doesn't seem too complicated and the feature would help considerably in semi-transparent setups. Here's one idea: the blur kernel could be introduced as an output configuration option.

Note: This feature (or its superset) has been already requested in #453 and #3380.