bash: `prefix-meta`

<Esc> runs the prefix-meta bash/readline command to "metafy" the next character typed.

That gives an alternate way to type lots of useful bash commands:

• <Esc>3- instead of <Meta-3>- to type 3 dashes
• <Esc>. instead of <Meta-.> to cycle through previous last arguments
• <Esc>^ instead of <Meta-Shift-6> to perform history expansion in place