Add Built-in Widgets

Built-in Widgets.-.md

@@ -0,0 +1,14 @@
+`Widget`'s provide an isolated struct which provides the contents to display in the provided `Size` on the terminal. Each `Widget` can control how and when to update their displayed contents.
+
+The following `Widget`'s are provided by `zterm`:
+
+- `RawText`
+- `Spacer`
+
+# RawText
+
+Pager `Widget` for the provided file. Mainly used for Debugging purposes.
+
+# Spacer
+
+Empty `Widget` that is supposed to remain empty and serve as a placeholder for corresponding areas of the terminal screen.