Batch of PRs closed to re-open

[lgalabru]

PRs:

• feat!: migrate @solana/pay to @solana/kit #283
• impl: gill/kit solana pay #272
• Solana Pay v1.2 specification #270
• doc: Add eCommerce reference implementation section to ReadMe #264
• Fix validateSPLTokenTransfer by filtering accounts with isSigner flag from multiSigners #255
• feat(validateTransfer): optional amount field & overloading of validateTransfer that returns amount #231

were closed during a repo migration.
I'll re-evaluate case by case and work and getting back on track.

[amilz]

can drop 272 (283 supercedes it)