Digits (#3073)

* Digits

* digits widget

* update requires str

* digits docs

* simplify

* tweak docs

* snapshot test

* change name

* simplify

* docs

* Update _digits.py superfluous import

* Update _digits.py docstring

* address review

* formatting

* Update tests/snapshot_tests/snapshot_apps/digits.py

Co-authored-by: Dave Pearson <davep@davep.org>

---------

Co-authored-by: Dave Pearson <davep@davep.org>

docs/examples/widgets/clock.py

@@ -0,0 +1,31 @@
+from datetime import datetime
+
+from textual.app import App, ComposeResult
+from textual.widgets import Digits
+
+
+class ClockApp(App):
+    CSS = """
+    Screen {
+        align: center middle;
+    }
+    #clock {
+        width: auto;
+    }
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Digits("", id="clock")
+
+    def on_ready(self) -> None:
+        self.update_clock()
+        self.set_interval(1, self.update_clock)
+
+    def update_clock(self) -> None:
+        clock = datetime.now().time()
+        self.query_one(Digits).update(f"{clock:%T}")
+
+
+if __name__ == "__main__":
+    app = ClockApp()
+    app.run()