Two small fixes for two small crater crashes

[Hoolean]

Hello! This is just a small one with QoL fixes for two crater-related crashes:

• Quote URL in reproduction command, to help parse sources with spaces in their name
• Create cache directory (~/.fontc_crater_cache) if it does not exist yet

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Both can be reproduced and tested by copying the reproduction command for 'Konkhmer Sleokchher.glyphs' from the hosted fontc_crater results and running it without a ~/.fontc_crater_cache directory present 💥

_{Note: this is a personal contribution independent of my employer, and so I've submitted from a fork under my personal profile and email to make this distinction}

[rsheeter]

Thanks!