doc/encoders: alphabetically list the encoders

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
(cherry picked from commit 934df3b0375743ae2b03168a4174edb9f88a6889)

Signed-off-by: Timothy Gu <timothygu99@gmail.com>

Conflicts:
	doc/encoders.texi
doc/decoders: document libopus decoder

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
(cherry picked from commit 7eb5288f17aad81d5bd1b4d3d46533e457df262c)

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
doc/muxers: Add AIFF doc

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
(cherry picked from commit 4ec46b1160eb549a551823c168905b43922add31)

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
doc/encoders: add libopus encoder doc

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
(cherry picked from commit 561e05136f1cbe28a79af1940aa137f70281eef4)

Signed-off-by: Timothy Gu <timothygu99@gmail.com>

Conflicts:
	doc/encoders.texi
doc/encoders: add libxvid doc

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
(cherry picked from commit 6b255e5e70c72aa59ff7aed74b4ee976223eb140)

Signed-off-by: Timothy Gu <timothygu99@gmail.com>

Conflicts:
	doc/encoders.texi