Represents a parameter to a CSI-based escaped sequence.
CSI escapes typically have the form: CSI 3 m, but can also
bundle multiple values together: CSI 3 ; 4 m. In both
of those examples the parameters are simple integer values
and latter of which would be expressed as a slice containing
[CsiParam::Integer(3), CsiParam::Integer(4)].
There are some escape sequences that use colons to subdivide and
extend the meaning. For example: CSI 4:3 m is a sequence used
to denote a curly underline. That would be represented as:
[CsiParam::ColonList(vec![Some(4), Some(3)])].
Later: reading ECMA 48, CSI is defined as:
CSI P … P I … I F
Where P are parameter bytes in the range 0x30-0x3F [0-9:;<=>?]
and I are intermediate bytes in the range 0x20-0x2F
and F is the final byte in the range 0x40-0x7E