Increase the coverage of API documentation

See #1364 -- rather than pull in specific classes, this pulls in every
publicly-documented item (function, class, type, "constant", etc) that can
be found in each of the modules.

This should help improve the linkage of types within the documentation.

docs/api/binding.md

@@ -1 +1 @@
-::: textual.binding.Binding
+::: textual.binding

docs/api/coordinate.md

@@ -1 +1 @@
-::: textual.coordinate.Coordinate
+::: textual.coordinate

docs/api/dom_node.md

@@ -1 +1 @@
-::: textual.dom.DOMNode
+::: textual.dom

docs/api/message.md

@@ -1 +1 @@
-::: textual.message.Message
+::: textual.message

docs/api/message_pump.md

@@ -2,4 +2,4 @@ A message pump is a class that processes messages.
 
 It is a base class for the `App`, `Screen`, and `Widget` classes.
 
-::: textual.message_pump.MessagePump
+::: textual.message_pump

docs/api/scroll_view.md

@@ -1 +1 @@
-::: textual.scroll_view.ScrollView
+::: textual.scroll_view

docs/api/strip.md

@@ -1 +1 @@
-::: textual.strip.Strip
+::: textual.strip

docs/api/widget.md

@@ -1 +1 @@
-::: textual.widget.Widget
+::: textual.widget