Deleting cache directory as a troubleshooting effort

[seancdavis]

Might be worth mentioning somewhere that one possible way to debug is to delete the .contentlayer directory and restart the server. But ideally users would also log issues along the way.

[seancdavis]

We may be better served to have a troubleshooting section including known issues.

This should also be worked in conjunction with #32

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If that's the path, let's address #33 first.