v0.21.6

## Important announcement

rtsp-simple-server is being rebranded as MediaMTX. Furthermore, my main open source projects are being transferred to the [bluenviron organization](https://github.com/bluenviron), in order to allow the community to maintain and evolve the code regardless of my personal availability.

## Fixes and improvements

General

* switch to go 1.19 (#1563) https://github.com/aler9/rtsp-simple-server/commit/45727a6de4d1d77666177d6191b3a281f9a1bae3
* support H265 SPS with long_term_ref_pics_present_flag (#1441)  (https://github.com/aler9/gortsplib/issues/197) https://github.com/aler9/gortsplib/commit/8be6bf735db83add5893aa50f35b6e1ea3ebb2d4
* prevent generating empty H264/H265 RTP packets (#1505) https://github.com/aler9/rtsp-simple-server/commit/bf691d168015702f32803cf93a8ced0140e9aedb
* docs: Fix webrtcICEServers format in README.md. (#1528) https://github.com/aler9/rtsp-simple-server/commit/167c5ec6c505990498d2e968c72563e93edcf792

RTMP server

* rtmp: fix panic when publishing audio-only streams (#1459) (#1502) https://github.com/aler9/rtsp-simple-server/commit/c7938eb832acc75193a10b744ce6f29a8bf1cb33
* rtmp: fix crash when receiving unexpected video packets (#1459) (#1504) https://github.com/aler9/rtsp-simple-server/commit/2cffea6d513a8df63d39878c5567e37262f285b3

HLS muxer

* hls: make hlsEncryption optional even with Low-latency variant (#1420) (#1530) https://github.com/aler9/rtsp-simple-server/commit/4e579702ed50301de2caaa8725b9d645636d69ba

Raspberry Pi Camera

* rpicamera: support libcamera 0.0.4 (#1544) (#1548) https://github.com/aler9/rtsp-simple-server/commit/695da99e228fa16cb944935e18cf206dcd074a6a
* rpicamera: fix segmentation fault with older Raspberry Pis and Docker (#1513) (#1549) https://github.com/aler9/rtsp-simple-server/commit/25dc252342b44971a731d8795cb3536213f8d797

HLS Source

* update gohlslib (#1565) https://github.com/aler9/rtsp-simple-server/commit/f4b9133bb86a0a04567d4674864ff4911dc87ce2