PSBT setup

[AadityaKhurana]

PSBT Implementation Setup

Overview

This PR establishes the initial setup for the PSBT (Partially Signed Bitcoin Transaction) implementation.

The psbt object is structured as a dictionary with the following format:

• global: Contains the global map
• input: A list of inputmaps
• output: A list of outputmaps

the psbt object follows the Specification given in BIP 174

Current Functionality

• Supports serialization (to bytes)
• Supports parsing (from bytes)
• Requires a provided globalmap, input, and output information

Future Enhancements

• Serialization and parsing in hex format
• Serialization and parsing in base64 (b64) format

Feedback

I would appreciate any feedback on:

• The overall length of the PR
• The level of detail needed in the documentation
• Any other suggestions or improvements

This will help improve future PRs.

I intend to expand this PR until we can create, update, and sign a PSBT.

[karask]

@AadityaKhurana

I will not look at any PSBT implementations until the proposals have been submitted.

[karask]

Proposals have finished and another PSBT design / implementation was selected.