Merge bitcoindevkit/bdk#1157: chore: pin `byteorder` and `webpki` to fix MSRV

1db3f87a4850c11b010ceafeba8a64ee0e54e022 chore: pin `byteorder` and `webpki` to fix MSRV (志宇)

Pull request description:

  * pin `byteorder` to 1.4.3
  * pin `webpki` to 0.22.2
  * it's tokio:1.33.0 that needs to be pinned to 1.29.1
  * fix README MSRV comments

ACKs for top commit:
  danielabrozzoni:
    utACK 1db3f87a4850c11b010ceafeba8a64ee0e54e022

Tree-SHA512: 4c2dc009ea117dd7ca18c7a836eb2b169c68d6ccaf84f85bcc2d4a3bcb7b008ad99f1dadf933b20c9d6ca6cc761e89dbafa99f99e31776e291f480cd6a112b1d