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 pylint-dev#9443.

doc/whatsnew/fragments/9443.feature

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

pylint/reporters/text.py

@@ -219,9 +219,9 @@ class ColorizedTextReporter(TextReporter):
     }
 
     def __init__(
-        self,
-        output: TextIO | None = None,
-        color_mapping: ColorMappingDict | None = None,
+            self,
+            output: TextIO | None = None,
+            color_mapping: ColorMappingDict | None = None,
     ) -> None:
         super().__init__(output)
         self.color_mapping = color_mapping or ColorizedTextReporter.COLOR_MAPPING
@@ -255,9 +255,16 @@ 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 = "::error file={path},line={line},endline={end_line},col={col},title={msg_id}::{msg}"
+
+
 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)