Update the BDK playground

[danielabrozzoni]

It's using a really old version of bdk-cli, and returning wrong descriptors (with the miniscript bug) when you use thresh. We should update it so that it uses the last bdk (we can't use bdk-cli anymore as it's not a library)

Also, maybe it would be cool to have the REPL in a completely separated page? So we can have a playground for experimenting with policies and descriptors, and a whole different page for trying out BDK.

[michaelfolkson]

I was using the BDK Playground to quickly see whether the Rust Policy/Miniscript compiler output matched the C++ Policy/Miniscript compiler output and was going to open an issue for this but Daniela beat me to it :)

[danielabrozzoni]

If you want to test it out, #118 should solve the issue :)