Third-party notices for the video encoder

The video encoder loads these components only when a user sends a video clip.

mediabunny 1.61.0
  License: Mozilla Public License 2.0 (https://mozilla.org/MPL/2.0/)
  Source: https://github.com/Vanilagy/mediabunny/tree/v1.61.0

@mediabunny/aac-encoder 1.61.0
  License: Mozilla Public License 2.0 (https://mozilla.org/MPL/2.0/)
  Source: https://github.com/Vanilagy/mediabunny/tree/v1.61.0/packages/aac-encoder

FFmpeg libavcodec 62.23.103 and libavutil (AAC encoder), compiled to WebAssembly in @mediabunny/aac-encoder
  License: GNU Lesser General Public License 2.1 or later (https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html)
  Source: https://github.com/FFmpeg/FFmpeg
  Build instructions: https://github.com/Vanilagy/mediabunny/blob/v1.61.0/packages/aac-encoder/README.md
  The encoder ships as its own file (assets/<build>/video-aac-encoder.<build>.chunk.min.js).
  To use a modified FFmpeg, rebuild the package with the build instructions above, then rebuild the application.