Select widget (#2501)

* overlay rule

* select WIP

* select control, made binding description optional

* changelog

* style tweak

* Added constrain

* changelog

* test fix

* drop markup, tidy

* tidy

* select namespace

* tests

* docs

* Added changed event

* changelog

* expanded

* tests and snapshits

* examples and docs

* simplify

* update reactive attributes

* type fix

* docstrings

* allow renderables

* superfluous init

* typing fix

* optimization

* revert optimizations

* fixed words

* changelog

* docstrings

* don't need this

* changelog

* comment

* Update docs/widgets/select.md

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

* review changes

* review updates

---------

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

docs/examples/widgets/select.css

@@ -0,0 +1,11 @@
+Screen {
+    align: center top;
+}
+
+Select {
+    width: 60;
+    margin: 2;
+}
+Input {
+    width: 60;
+}

docs/examples/widgets/select_widget.py

@@ -0,0 +1,26 @@
+from textual import on
+from textual.app import App, ComposeResult
+from textual.widgets import Header, Select
+
+LINES = """I must not fear.
+Fear is the mind-killer.
+Fear is the little-death that brings total obliteration.
+I will face my fear.
+I will permit it to pass over me and through me.""".splitlines()
+
+
+class SelectApp(App):
+    CSS_PATH = "select.css"
+
+    def compose(self) -> ComposeResult:
+        yield Header()
+        yield Select((line, line) for line in LINES)
+
+    @on(Select.Changed)
+    def select_changed(self, event: Select.Changed) -> None:
+        self.title = str(event.value)
+
+
+if __name__ == "__main__":
+    app = SelectApp()
+    app.run()