Downloader downloads into src dir, which is not synced with the venv dir.

[G3zz]

Steps to reproduce:

1. Delete replay resources in src/astro_pi_replay/resources/replay/VIS/*
2. Delete venv in ~/.astro_pi_replay
3. Install the AstroX sequence (Astro-Pi-Replay download --sequence AstroX)
4. Run Astro-Pi-Replay run examples/picamzero/basic_photo.py - this will recreate the venv in ~/.astro_pi_replay.
5. Install the videos for the sequence (Astro-Pi-Replay download --sequence AstroX --with-video)
6. Run Astro-Pi-Replay run examples/picamzero/video_fixed_duration.py`

This will fail because the ~/astro_pi_replay venv will be missing the installed video folder.

[G3zz]

I've been thinking for a while to move the resource dir to the ~/.astro_pi_replay dir under assets - this is one option.
Another option is to sync up the src and venv folders on each run...