[vim] Add support for :sort

Supports all options except [r] and [/pattern}/].
```
							*:sor* *:sort*
:[range]sor[t][!] [i][u][r][n][x][o] [/{pattern}/]
			Sort lines in [range].  When no range is given all
			lines are sorted.

			With [!] the order is reversed.

			With [i] case is ignored.

			With [n] sorting is done on the first decimal number
			in the line (after or inside a {pattern} match).
			One leading '-' is included in the number.

			With [x] sorting is done on the first hexadecimal
			number in the line (after or inside a {pattern}
			match).  A leading "0x" or "0X" is ignored.
			One leading '-' is included in the number.

			With [o] sorting is done on the first octal number in
			the line (after or inside a {pattern} match).

			With [u] only keep the first of a sequence of
			identical lines (ignoring case when [i] is used).
			Without this flag, a sequence of identical lines
			will be kept in their original order.
			Note that leading and trailing white space may cause
			lines to be different.

			When /{pattern}/ is specified and there is no [r] flag
			the text matched with {pattern} is skipped, so that
			you sort on what comes after the match.
			Instead of the slash any non-letter can be used.
			For example, to sort on the second comma-separated
			field:
				:sort /[^,]*,/
 			To sort on the text at virtual column 10 (thus
			ignoring the difference between tabs and spaces):
				:sort /.*\%10v/
 			To sort on the first number in the line, no matter
			what is in front of it:
				:sort /.\{-}\ze\d/
 			(Explanation: ".\{-}" matches any text, "\ze" sets the
			end of the match and \d matches a digit.)
			With [r] sorting is done on the matching {pattern}
			instead of skipping past it as described above.
			For example, to sort on only the first three letters
			of each line:
				:sort /\a\a\a/ r

 			If a {pattern} is used, any lines which don't have a
			match for {pattern} are kept in their current order,
			but separate from the lines which do match {pattern}.
			If you sorted in reverse, they will be in reverse
			order after the sorted lines, otherwise they will be
			in their original order, right before the sorted
			lines.

			If {pattern} is empty (e.g. // is specified), the
			last search pattern is used.  This allows trying out
			a pattern first.
```