v0.2.2

Added

• servicekit/http/webhooks signs and verifies Standard Webhooks v1
  deliveries: Sign, Verify (accepts any of several space-separated
  signatures), TimestampWithinTolerance, GenerateSecret and
  ValidateSecret for whsec_ secrets. The HMAC key is the decoded secret, as
  the spec says. It is standard library only, and matches the spec's test
  vector and the reference Go library. It moved from mcpkit's
  experimental/ext/events (mcpkit#1578, PR 59).