docs: Update PatternMatchingEventHandler documentation (#1048)

* Update PatternMatchingEventHandler documentation

From the existing docs it's not clear what the difference is between
PatternMatching and RegexMatching. Hopefully this makes it clearer.

Also made a note that RegexMatching uses the re module, since there are
various flavors of regex syntax and it's important to know which one is
used.

* Apply suggestions from code review

---------

Co-authored-by: Mickaël Schoentgen <[email protected]>

src/watchdog/events.py

@@ -297,6 +297,8 @@ def on_opened(self, event: FileSystemEvent) -> None:
 class PatternMatchingEventHandler(FileSystemEventHandler):
     """
     Matches given patterns with file paths associated with occurring events.
+    Uses pathlib's `PurePath.match()` method. `patterns` and `ignore_patterns`
+    are expected to be a list of strings.
     """
 
     def __init__(
@@ -375,6 +377,7 @@ def dispatch(self, event: FileSystemEvent) -> None:
 class RegexMatchingEventHandler(FileSystemEventHandler):
     """
     Matches given regexes with file paths associated with occurring events.
+    Uses the `re` module.
     """
 
     def __init__(