added wp & file cache
when fetching the shell:
- look in the wp cache for the shell and if it exists, use it
- if the cache doesn’t exist, try to get a fresh version of the shell and save it locally to a file in ‘public/content/cache/wa-shell/shellurl.com.json’
- if the shell cannot be fetched, look locally for a file containing the shell in
public/content/cache/wa-shell/shellurl.com.json - save the file contents in the cache