add an arg to list the installed scrapers

[bachig26]

Describe the feature/change you'd like.
at the moment, the plugins has it's default scrapers, so we're calling it just using the keyword like films, youtube, etc.
but if the default scraper doesn't work. most people using don't remember having other scrapers available and one needs to look through the plugins repo or most of will open an issue.

if an arg specifically available to list out the installed/available scrapers in the plugins, will make it easier to use without exiting the terminal.
for example, after calling the arg in mov-cli like mov-cli --list-scrapers or mov-cli -ls;
then it could show the available scrapers like below:

films
{namespace}.{scraper}
{namespace}.{scraper}

youtube
{namespace}.{scraper}

anime
{namespace}.{scraper}
{namespace}.{scraper}

might be useful also by indicating which one is the default scraper now.

[r3tr0ananas]

I'll look in to it.

[r3tr0ananas]

Will be added with v4.3.

[r3tr0ananas]

0632aad