2.3.0

Release Nageru and Futatabi 2.3.0.

  - Support SRT output of the encoded stream, including
    output to YouTube if your account is enabled for this
    (beta testers only as of this release). This is useful
    for push, and for bad networks (e.g. 4G).

  - Fix various deprecation warnings with newer FFmpeg
    (Nageru should now be warning-free with FFmpeg 6.0).
    This also means that Nageru now requires FFmpeg 5.1
    or newer.

  - Fix crashes with newer SVT-AV1.