Attach pow to notes

[ticruz38]

• Generate a PoW for notes and replies
• Hide notes based on the PoW difficulty (configurable in app settings)
• User Settings to attach a PoW difficulty with each send
• Note option to adjust the PoW difficulty before send
• Note Create loading state is now richer, it is either signing, or generating a PoW
• The PoW generation is done in a web worker to avoid the main thread to lock up completely

I had a strange issue when developing this PR, the Worker class, which is a browser native API, was set to the Welshman Worker class, instantiating the PoW worker would just create another welshman Worker class. It might be due to how I link welshman. Let me know if you have that same issue as well.

[ticruz38]

#86

[staab]

Looks good on first review, haven't tested it yet.

I had a strange issue when developing this PR, the Worker class, which is a browser native API, was set to the Welshman Worker class, instantiating the PoW worker would just create another welshman Worker class. It might be due to how I link welshman. Let me know if you have that same issue as well.

This is because in App.svelte line 320 I'm assigning everything in welshman to window for convenience when using the console. You can remove the lib assignment and it should fix the issue.