Expanded bits literals

[foxfriends]

Support a wider range of bits literals.

Either look like a template tag:

• $b"hello"
• $b'c'

Or look like a bits number literal but it's a string instead:

• 0b"hello"
• 0b'c'

Likely template tag is better, as we might want to support various encodings:

• $ascii"hello"
• $utf16"hello"

Though... other than tagged characters (arguably useless), these could all be implemented at runtime as template tags (and call to_bits on interpolated values too?).