Pymtheg

Dependency bump + documentation updates

Fix timestamp bugs + implement end-relative timestamps + quality of use updates

- theoretically fixed the `-cs "*" -ce "*"` bug
- 0 timestamps would show empty during confirmations
- invalidate -1 as a start timestamp
- new end-relative timestamp parsing, e.g. -15
- not show error message if all songs were skipped

Fixed random timestamp bug + quality of use updates

- grouped command line options into "clip", "output", "tool" and "pymtheg"
- fixed bug where if -cs and -ce were "*" (random), they may be the same and cause a failure in ffmpeg invocation
- allow local files to be specified in queries, placeholder cover art to be used if not available
- add -sm, --save-music and -smd, --save-music-dir to allow downloaded music to be saved
- use rich for traceback formatting
- show full invocation for all errors
- fix random timestamps being misrepresented as "0"

Added a timestamp exclusion argument + minor changes/updates

- added `-nt, --no-timestamp` to exclude timestamp from output clip paths
- not show song duration if defaults are being used (-ud, --use-defaults)
- updated deps

Update READMEs to show new minimum Python version

Quality of use updates + minor code fixes/changes

- removed unused import
- add explanatory text for {cer} placeholder in --help
- added examples to pymtheg --help
- removed extra space in using defaults text, standardised usage of " for representing text in text
- reworked timestamp handling to ensure that e.g. `-cs "*" -ce "+15"` will always be `+15` seconds
- fix timestamp confirmation not appearing sometimes
- show song duration alongside song name
- 0 left strip confirmation timestamps/file name timestamps/song duration
- fix text formatting for invalid clip start/end messages during command line argument validation
- update spotdl to 3.9.4
- update rich to 12.2.0
- minimum python version is now 3.6.3