Add GitHub reporter

A new `github` reporter has been added. This reporter automatically
annotates code on GitHub's UI with the messages found during linting.

Closes #9443.

Author: crazybolillo

doc/whatsnew/fragments/9443.feature

@@ -0,0 +1,4 @@
+A new `github` reporter has been added. This reporter automatically annotates code on GitHub's user interface
+with the messages found during linting. Use it with `pylint --output-format=github`.
+
+Closes #9443.

pylint/reporters/text.py

@@ -255,9 +255,32 @@ def handle_message(self, msg: Message) -> None:
         self.write_message(msg)
 
 
+class GithubReporter(TextReporter):
+    """Report messages in GitHub's special format to annotate code in their UI."""
+
+    name = "github"
+    line_format = "::{category} file={path},line={line},endline={end_line},col={column},title={msg_id}::{msg}"
+
+    def write_message(self, msg: Message) -> None:
+        self_dict = asdict(msg)
+        for key in ("end_line", "end_column"):
+            self_dict[key] = self_dict[key] or ""
+
+        msg_type = msg.msg_id[:1]
+        category = "error"
+        if msg_type == "W":
+            category = "warning"
+        elif msg_type in {"C", "R", "I"}:
+            category = "notice"
+
+        self_dict["category"] = category
+        self.writeln(self._fixed_template.format(**self_dict))
+
+
 def register(linter: PyLinter) -> None:
     linter.register_reporter(TextReporter)
     linter.register_reporter(NoHeaderReporter)
     linter.register_reporter(ParseableTextReporter)
     linter.register_reporter(VSTextReporter)
     linter.register_reporter(ColorizedTextReporter)
+    linter.register_reporter(GithubReporter)