Add run0 parser

I tested this parser using this script:

	#!/usr/bin/env bash

	run0 \
		-h --help \
		-V --version \
		   --no-ask-password \
		   --machine=CONTAINER \
		   --unit=UNIT \
		   --property=NAME=VALUE \
		   --description=TEXT \
		   --slice=SLICE \
		   --slice-inherit \
		-u USER --user=USER \
		-g GROUP --group=GROUP \
		   --nice=NICE \
		-D PATH --chdir=PATH \
		   --setenv=NAME \
		   --background=COLOR \
		   --pty \
		   --pipe \
		   --shell-prompt-prefix=PREFIX \
		hello

	run0 \
		-h --help \
		-V --version \
		   --no-ask-password \
		   --machine=CONTAINER \
		   --unit=UNIT \
		   --property=NAME=VALUE \
		   --description=TEXT \
		   --slice=SLICE \
		   --slice-inherit \
		-u USER --user=USER \
		-g GROUP --group=GROUP \
		   --nice=NICE \
		-D PATH --chdir=PATH \
		   --setenv=NAME \
		   --background=COLOR \
		   --pty \
		   --pipe \
		   --shell-prompt-prefix=PREFIX \
		-- \
		hello

	run0 -- run0 -- hello
	run0 run0 hello
	run0
	run0 -u hello hello

I was able to successfully resholve that script by running this command:

	NIX_CONFIG='extra-experimental-features = nix-command flakes' nix run <path to resholve repo>#resholve-with-packages -- <path to script> systemd hello

Author: Jayman2000

resholve

@@ -2579,6 +2579,57 @@ class ExternalCommandParsers(object):
 
         return (generic,)
 
+    @staticmethod
+    def _run0():
+        """
+        This was based on running "run0 --help" with systemd v257.6.
+
+        This was also based on some manual testing because the "--" argument
+        wasn't documented [1].
+
+        [1]: <https://github.com/systemd/systemd/issues/37961>
+        """
+        generic = CommandParser("run0")
+        generic.add_argument(
+            "-h",
+            "--help",
+            "-V",
+            "--version",
+            "--no-ask-password",
+            action="store_true"
+        )
+        generic.add_argument(
+            "--machine",
+            "--unit",
+            "--property",
+            "--description",
+            "--slice",
+            nargs=1
+        )
+        generic.add_argument("--slice-inherit", action="store_true")
+        generic.add_argument(
+            "-u",
+            "--user",
+            "-g",
+            "--group",
+            "--nice",
+            "-D",
+            "--chdir",
+            "--setenv",
+            "--background",
+            nargs=1
+        )
+        generic.add_argument(
+            "--pty",
+            "--pipe",
+            action="store_true"
+        )
+        generic.add_argument("--shell-prompt-prefix", nargs=1)
+        generic.add_argument(
+            "commands", nargs="*", action="invocations"
+        )
+        return (generic,)
+
 
 def generate_builtin_command_parser(cmdname):
     cmdname = "_" + cmdname