feat: Add built-in to search keymaps (#191)

* Add built-in to search keymaps

* Re-factor maps for cleaner codes

Rather than use function to return a results table for various key maps.
Assign results the key maps table itself. This makes for cleaner code.

* Keymaps: escape termcodes using built-in util

* Rename builtin.maps to builtin.keymaps

README.md

@@ -345,6 +345,13 @@ require'telescope.builtin'.command_history{}
 
 Search the vim command history.
 
+```lua
+require'telescope.builtin.maps{}
+```
+
+Search on vim key maps.
+
+
 ```lua
 require'telescope.builtin'.buffers{
     -- Optional