feat: add PR update notifications

[kaijianding]

implement #25

and fix hide inactive pr preference doesn't work

[SeanMcTex]

Hey @kaijianding -- sorry for the delay on this. Looking at the PR diff, it seems as though there's a lot of spurious info included in the PR. Could you please rebase this or create a new branch and cherry pick the relevant work so that I can dig into just the code that's actually part of this change? Thanks!

[kaijianding]

Hey @kaijianding -- sorry for the delay on this. Looking at the PR diff, it seems as though there's a lot of spurious info included in the PR. Could you please rebase this or create a new branch and cherry pick the relevant work so that I can dig into just the code that's actually part of this change? Thanks!

There are 3 parts

1. update check itself
2. add notification text in setting
3. register notification

Do you mean remove the second and third part, remain only the first part? @SeanMcTex