feat(cookbook): PSBTs multiple inputs

[storopoli]

Adds examples on how to create, update, sign, and finalize PSBTs version 0 that deals with multiple inputs.

Examples are SegWit V0 and Taproot.

• updates CI to capture all nested *.md files
• PSBT introduction
• SegWit V0
• Taproot

Closes #26.

[storopoli]

Ready to review guys!

[storopoli]

The new examples are in a nested dir inside src/.
That's why this change

[tcharding]

I started reviewing but then realised, while struggling with reviewing code in either the markdown file or the rendered HTML, that for the other cookbook stuff I did a PR into rust-bitcoin/bitcoin/examples first.

Any chance you would be willing to do that also, then we can review the code like normal and copying it to the cookbook is just a matter of cut'n'pasting the relevant bits.

[storopoli]

Any chance you would be willing to do that also, then we can review the code like normal and copying it to the cookbook is just a matter of cut'n'pasting the relevant bits.

Yes of course!
That was my original idea.
I just thought that since this is a VERY stripped down of
bitcoin/examples/ecdsa-psbt.rs
and bitcoin/examples/taproot-psbt.rs,
that they would not be "worth" of an example in rust-bitcoin.

That's why I PR'd here only and first.
But yeah I'll work on a code + comments version of these in rust-bitcoin.
That's a great suggestion and thanks for encouraging it.

[tcharding]

ACK 81c90e6