keep the "pinned" attribute of the side web panel and the button in sync

[mokazemi]

I just added pinned="true" attribute to web panel pin icon, so that its initial state matches with the panel state.
Also added a function to keep the pinned state of the side web panel and the button in sync.

fixes: #4322

[mauro-balades]

What if the initial state isn't pinned? I feel like this is a cheap solution to a bigger underlying problem. Where the check isnt being ran on initialization

[mokazemi]

What if the initial state isn't pinned? I feel like this is a cheap solution to a bigger underlying problem. Where the check isnt being ran on initialization

Oh, you're right. I should work more on it to see if I can do anything about it. I'm not much a JS developer but I guess I know where the issue is comming from. Maybe defining an init function that syncs the state of the panel with the icon state would solves the issue.

[mokazemi]

I changed it to change the pin icon based on if the panel is pinned or no. @mauro-balades
I checked all three states (initial run, when the panel is unpinned last time, when the panel is pinned last time). It seems to work in all these conditions.