Various fixes for shortcodes and stability

[illgitthat]

I made a few changes on my own fork and wanted to contribute back in case this is still being maintained @dzg.

• Introduces a fix for issue Inbound text messages from shortcodes are not supported #7 (short codes)
• Improved the extraction of text from email subjects. This includes better handling of short codes and cases where the number is not found in the subject line.
• Introduced a new imapSearchFolder configuration parameter. This allows the user to specify a different folder to search for messages, which can be useful if Google Voice emails are automatically archived.
• Added an example method to run the script using forever in service.sh

I can't guarantee code quality here, but I thought it made sense to open a PR at this point as it solved a few issues I was having.

[dzg]

Thanks! Good stuff!
I don't really use Beeper any more so I won't be very active here.

[dzg]

Oh and – if you're up to it – someone changed the auth method to xoauth2 over at
JackHMcD@2adbcd4

... which is probably a much better (more secure) method than app passwords.

Maybe you have the werewithal to integrate that!