Doom Converter media engine notices

@ffmpeg/ffmpeg 0.12.15: MIT. Copyright (c) 2019 Jerome Wu.
License: WRAPPER-MIT.txt
@ffmpeg/core 0.12.10: GPL-2.0-or-later (upstream package declaration).
License: CORE-GPL-2.0.txt

The unmodified upstream ESM core and WASM are used. The WASM is split into
three transport parts, then reassembled byte-for-byte before execution.
No codec source is changed. The core runs in a separate worker.

Core release source, including Dockerfile, bindings and build scripts:
https://github.com/ffmpegwasm/ffmpeg.wasm/tree/71aa99d37c02a7b4c435275ca9ef50e612f6efa1
Download the build source:
https://codeload.github.com/ffmpegwasm/ffmpeg.wasm/tar.gz/71aa99d37c02a7b4c435275ca9ef50e612f6efa1

Component source archives and original copyright/license notices are linked
in /licenses/ and sources.json in this directory. The versions follow that
release's Dockerfile, including upstream branch references where the recipe
uses branches. Archive SHA256 values identify the retrieved sources.
The recipe uses emscripten/emsdk:3.1.40, including the SDL2 port:
https://github.com/emscripten-core/emscripten/tree/3.1.40
https://github.com/emscripten-core/emscripten/blob/3.1.40/LICENSE
https://github.com/emscripten-ports/SDL2

These components are provided under their respective licenses, without
warranty. See each full license for permissions, conditions and disclaimers.