feat: add configurable window shade callback

[yujinyuz]

Closes #20

[yujinyuz]

@miversen33 Still need to update the documentation.

Let me know what you think about the function callback name. I couldn't think of anything better atm.

[miversen33]

@yujinyuz are you still working on this? If not, I am going to close the PR out

[yujinyuz]

@miversen33 I'm not actively working on it since I don't have enough bandwidth.

I'm just using this PR's version in my local since it works for my use case.

Feel free to close this PR

[miversen33]

Closed in favor of #28