periodically re-index/watch for changes

[Ivshti]

for unix, this can be done via fs.watch

for mac, there is a mdfind flag we can use

for windows, god knows

[Ivshti]

alternatively we can just re-do the entire scan every 24 hours, which seems to be much more reasonable

however, we'd be missing use cases like downloading content and having it detected immediately, but there's no way in the addon protocol to make stremio refresh the results anyway

just for the local add-on we can just re-poll the result of /catalog/* every 60 seconds or so