Update rsa modulus endianess to match most protocols

[matheus23]

Most protocols encode the RSA modulus in big-endian format.
E.g.

• JWK spec (see also Section 2 "Terminology" and Base64urlUInt encoding)
• ASN.1 DER RSAPublicKeys are encoded as ASN.1 DER INTEGERs. The best reference I found was this stackoverflow answer :/ but I can confirm from working with the encoding in the past for ts-ucan.

❗ merge order ❗

1. This PR
2. Remove namefilter.md and add NameAccumulator verification algorithm #68
3. Specify Blake3's derive_key algorithm instead of SHA3 #69
4. Switch from AES-GCM to XChaCha20-Poly1305 #70
5. Add baseName to ExternalContent #71

[expede]

Just the one suggestion, but LGTM! 🚢