SwiftNIO HTTP/2 1.19.2

The release contains fixes for three security vulnerabilties.

SemVer Patch

• CVE-2022-24668: Denial of service via ALTSVC or ORIGIN frames
• CVE-2022-24667: Denial of service via mishandled HPACK variable length integer encoding
• CVE-2022-24666: Denial of service via invalid HTTP/2 HEADERS frame length

Other Changes

• Update doc generation script (#322)
• Add 5.6 nightly CI (#324)