feat: new symbolic icons for effects

[yioannides]

As part of #2091 and #2120 ~

[Skif-off]

Does effects-artistic-pencilsketch-symbolic.svg really look okay in a light theme?
Bright acidic color, without clear boundaries...

[yioannides]

We haven't discussed about the backend for icon colorization and color profiles, right now the colors are hardcoded as a placeholder and could be changed at any time. The plan is for colors to be optional though, so if you don't like the colors, you will be able to disable them.

[Skif-off]

so if you don't like the colors, you will be able to disable them.

I don't mean the colors, but the chosen color of this particular icon :)

[yioannides]

As I said, the colors are subject to change. We could try --yellow-5 instead of --yellow-4, but I think it's a matter of taste and --yellow-4 looks perfectly fine in light mode and 16x16 resolution when we tested it, so we could potentially defer darker colors to a "high contrast" color profile, when the time comes. I will keep the icon as is for now.

--yellow-4	--yellow-5