Update readme with implemented specs

Unblock blocking writes on close

Implement SCTP Negotiation Acceleration Protocol (SNAP) (#449)

This commit adds a createAssociationWithOutOfBandTokens method
that creates the SCTP association with a local and remote sctp-init
token as described in draft-hancke-tsvwg-snap-00.

Tokens can be generated using the newly added GenerateOutOfBandToken
method and set in the sctp.Config as LocalSctpInit and RemoteSctpInit.

This allows the peer connection to generate and negotiate the
sctp-init attribute in the SDP which skips two network round trips.

See https://datatracker.ietf.org/doc/draft-hancke-tsvwg-snap/

Fixed shutdown race where ABORT is not sent (#456)

Fix a shutdown race where Association.Abort() could return without
the ABORT being written, which in turn can delay peer-side close
detection (e.g. webrtc.SCTPTransport.OnClose) and cause intermittent
timeouts.

Exit fast recovery outside guard

Upgrade to pion/transport/v4

Fix RACK recording time for all segments

Fix a deadlock with Abort

Fix a deadlock with write and read on abort.
more likely to happen with tcp.

Co-authored-by: boks1971 <raja.gobi@tutanota.com>

Retract v1.8.12 due to ZeroChecksum misinterpretation (#398)

Allow MTU to be set via Config