Expose uri params label message

[riverKanies]

Closes #48

We want to expose standard bip21 params on the Uri type so that it can be used as a bip21 module in apps.
Note that this pr points to an updated version of payjoin-ffi that exposes the params (label + message).

The dependency on payjoin-ffi has been updated to point to the main payjoin-ffi repo

Note: locally I had to make some other changes just to get the example running, they are included in a separate commit that should not be merged

[riverKanies]

it'd make sense to merge this first #51
then rebase this pr onto that (to get rid of the 'do not merge' commit on this pr)

[riverKanies]

Ok this has been rebased an is ready for merge now I believe @DanGould
Once we get this merged we can make a release and update the bullbitcoin dependency.

unfortunately one of the deps updates somehow slipped through the other pr and so the change to fix the RFB version to 2.0.0 is in this PR. I know that I was having an issue with the non-specific version for RFB so I fixed it and everything works for me with this change

[DanGould]

Exposing label and message seems right. As noted in the past PR your commit messages must adhere to a certain standard.

Are you sure the first commit is right? Wouldn't a change to deps update podspec.lock, or is it already using 2.0.0?

The first commit message says 'sever' instead of 'severe' as well. perhaps "Make RFB version fixed to avoid v conflicts" > "Fix FRB version to avoid conflilcts"?

[riverKanies]

I'm going to retest that dep fixing, probably unnecessary. I think I actually reverted in when I split the PR in two.

I'm also going to update the payjoin_ffi version to the release

[riverKanies]

@DanGould we never actually made a tag for v0.22.1
Do you want to make one real quick so that I can use that as the dep for this pr?

[DanGould]

No reason to tag since we won't do an 0.22.1 release, and bull bitcoin isn't using proper releases anyhow, and they'll upgrade to 0.23. Just use the commit hash so we can progress

[riverKanies]

using the following to test locally:

final pjUri = await pjuri.Uri.fromStr(
        "bitcoin:tb1p6ah70934hd3ppw6f5j9der7vdgz2zz92nxcspyuxqcntqpgjny2se7mals?amount=0.00008&label=mylabel&pjos=0&pj=HTTPS://PAYJO.IN/Q40QVRA849287%23RK1Q20SPY3G2Y0H6CKZX25ERJHDJ4HLETX3SC5UMZPKFJK0L73D2AY6G+OH1QYPM59NK2LXXS4890SUAXXYT25Z2VAPHP0X7YEYCJXGWAG6UG9ZU6NQ+EX1YL32GEC");
    debugPrint(pjUri.label());

[riverKanies]

ok should be good to go

[riverKanies]

ok I removed the readme updates, but this is something I find myself looking up every time I run the app so I'd like it to be in here

Simulator is the xcode simulator app. you have to have an instance already running for flutter to see it as a deploy target

[riverKanies]

@DanGould ready to merge? Once merged this is up to date with the bb dep so this repo can be upgraded with persistence and that can be added to bb next