Update README title and add logo & badges

[thebrandonlucas]

Update the README header to add a little more pizzaz. Specifically:

• Changes "Rust-Payjoin" title to "Payjoin Dev Kit"
  since that is the colloquial term we use

• Adds "static" directory for images and places
  the Payjoin "monad" logo in it

• Adds badges for: License, code coverage, Discord chat,
  MSRV, and CI

There are still a couple pieces of information I need to complete this:

• The Discord needs to be updated to enable the shields.io widget.
• I believe coveralls is already setup and working for payjoin as it's displaying 82% coverage when attached to the payjoin repo, but this needs to be verified.

[coveralls]

Pull Request Test Coverage Report for Build 14652272719

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 81.804%

---

Files with Coverage Reduction	New Missed Lines	%
payjoin/src/send/mod.rs	2	94.46%

Totals
Change from base Build 14519980933:	-0.03%
Covered Lines:	5323
Relevant Lines:	6507

---

💛 - Coveralls

[DanGould]

Going to squash these two commits and merge when ready

"Rust-payjoin" changing to "Payjoin Dev Kit" in the title suggests another readme specifically for the payjoin crate may be more appropriate. To avoid that, I'd rather follow rust-bitcoin's lead here since our repo and org are payjoin and not payjoindevkit and leave it as Rust Payjoin

The discord SERVER_ID is 1120791584674435134 (in the url. try that. don't see 'widget' in settings anywhere

I'd rather leave the license off (technically MIT NFA) and put crates.io and docs.rs links instead

[thebrandonlucas]

Going to squash these two commits and merge when ready

Apologies for the double commit, fixed now.

"Rust-payjoin" changing to "Payjoin Dev Kit" in the title suggests another readme specifically for the payjoin crate may be more appropriate. To avoid that, I'd rather follow rust-bitcoin's lead here since our repo and org are payjoin and not payjoindevkit and leave it as Rust Payjoin

Done

The discord SERVER_ID is 1120791584674435134 (in the url. try that. don't see 'widget' in settings anywhere

Unfortunately I tried that and I'm seeing "chat widget disabled". I do think there is something that we need to enable in Discord settings for this. According to shields.io, which hosts these badges, you can enable the widget by going to "Server Settings" -> "Widget" -> "Enable Server Widget". Is that no longer there?

Happy punt that one badge addition if it's too much effort for the payoff right now.

I'd rather leave the license off (technically MIT NFA) and put crates.io and docs.rs links instead

License removed, crates.io and docs.rs added, good call.

[DanGould]

haven't been able to get the discord widget setting to come up on the server :/. Maybe just drop that for now but otherwise LGTM. Thanks for the patience with review and the back and forth

[thebrandonlucas]

haven't been able to get the discord widget setting to come up on the server :/. Maybe just drop that for now but otherwise LGTM. Thanks for the patience with review and the back and forth

Discord badge removed, ready to go!

[DanGould]

ACK the CI is failing because of something unrelated