Add regression tests

[lidel]

We should have a test for each:

• CIDv0 (QmbWqxBEKC3P8tqsKc98xmWNzrzDtRLMiMPL8wBuTGsMnR)
• CIDv1 base32
  • dag-pb
  • raw
  • dag-json
  • dag-cbor
• CIDv1 base36
  • libp2p-key codec
• PeerID (not a CID, but pasting 12D3KooWJHxkQKX8C5KAyqEPhn2ssT2in4TExyG9SXxi519tycL9 should show meaningful error as noted in Support legacy (raw) PeerIDs in Base58btc #48)