preview cache

[qkzk]

/tmp/fm_preview_cache/

for each ueberzug preview -> preview_filename = hash(filepath) + {1-5}.[jpg/png]

visu :

cache get or create

caching :

• create a pool of workers
• each worker preview a file until full folder is done
• limit cache size & clear older than ...
• they stay dormant while nothing to preview
• use async + tokio

[qkzk]

done in v0.1.32 which is the next release