feat(cli): add static dir file discovery depth flag

[DanielSwarup]

• Added the flag --staticDirFileDiscoveryDepth which enables the user to set the depth of search for index.html files on a static site folder.

Reason For this feature:
When I ran lhci autorun on my static site folder which has deeper folders with index.html it did not recognise them after a depth of 2 folders. This is because LHCI currently hard caps it at a depth of 2. I hope the example in the docs changed file explains it.

(This is my first open-source contribution ever. Thank you for this amazing repo!)

[connorjclark]

Thanks!

I'm not sure why we have this limit in the first place ... but if we must have it, making it configurable is cool.

[DanielSwarup]

Thanks for fixing the linting error! I'll take a look at this test error and push asap.

[connorjclark]

You should just need to run yarn test:unit -u to update the snapshot tests.

[DanielSwarup]

Weirdly enough I've got a bunch of snapshots failing cause chromium is acting up. Could you please update the snapshot? Apologies and thank you!