fixes #341

- use codeigniter4/tasks project to handle cron tasks
- use yassinedoghri/podcast-feed project to parse feeds for imports

update composer dependencies to latest

refs #321

Users may choose between filesystem (FS) or S3 to store and manage their media files

closes #225

- update CI4 to v4.1.9's stable production package
- update php and js dependencies to latest

- rename podlibre to adaures
- rename castopod-host to castopod
- simplify README and redirect to docs site
- move INSTALL and UPDATE docs
- add new gitlabci pipeline to deploy docs
- upgrade node to v16 in Dockerfile

- tempfile uniqueness ensures that each process lives in its independent context
- add
writable/temp folder to store video clips temporary resources
- add videoClipWorkers config to
Admin for specifying the number of ffmpeg processes to run in parallel
- update video clip preview
background to better suit the end result

fix video colors to portray exact rgb values using libx264rgb encoding + image transparency issue
when overlaying images with php gd