Screencast: Convert to format suitable for GitHub Issues and Twitter

This format (720p produced by YouTube) is suitable for GitHub Issues and for Twitter. How can we convert our screencasts to it without the need for going via YouTube? I need the exact fffmpeg commands needed to convert existing video into this format.

```
FreeBSD% ffmpeg -i '/home/user/Desktop/Format suitable for Twitter.mp4' -f null -
ffmpeg version 4.4 Copyright (c) 2000-2021 the FFmpeg developers
built with FreeBSD clang version 10.0.1 (git@github.com:llvm/llvm-project.git llvmorg-10.0.1-0-gef32c611aa2)
(...)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/user/Desktop/Format suitable for Twitter.mp4':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
encoder : Google
Duration: 00:01:38.94, start: 0.000000, bitrate: 314 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 182 kb/s, 29.86 fps, 29.86 tbr, 29861 tbn, 59.72 tbc (default)
Metadata:
handler_name : ISO Media file produced by Google Inc.
vendor_id : [0][0][0][0]
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
Metadata:
handler_name : ISO Media file produced by Google Inc.
vendor_id : [0][0][0][0]
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> wrapped_avframe (native))
Stream #0:1 -> #0:1 (aac (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
Output #0, null, to 'pipe:':
Metadata:
major_brand : mp42
minor_version : 0
compatible_brands: isommp42
encoder : Lavf58.76.100
Stream #0:0(und): Video: wrapped_avframe, yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.86 fps, 29.86 tbn (default)
Metadata:
handler_name : ISO Media file produced by Google Inc.
vendor_id : [0][0][0][0]
encoder : Lavc58.134.100 wrapped_avframe
Stream #0:1(und): Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s (default)
Metadata:
handler_name : ISO Media file produced by Google Inc.
vendor_id : [0][0][0][0]
encoder : Lavc58.134.100 pcm_s16le
```