[bashrc] add autoupdate check + notification + autoupdate script (like zshrc)

[zudsniper]

Add the following convenience features to keep this script's users informed, and offer easy updates.
^{These things are already implemented in /.zshrc so check that out for the specifics -- it should be identical.}

• check for updates from bashrc.zod.tf
• compare versions -> if remote > local, show update notification which includes both remote & local versions, as well as the command to autoupdate.
• add autoupdate script which copies remote to local.

won't be hard, just need to do it.