feat: layout horizontal and vertical can now be mirrored (#548)

See documentation for more info

doc/telescope.txt

@@ -236,7 +236,8 @@ All layout strategies are functions with the following signature: >
         - columns : number Columns in the vim window
         - lines   : number Lines in the vim window
 
-TODO: I would like to make these link to `telescope.layout_strategies.*`, but it's not yet possible.
+TODO: I would like to make these link to `telescope.layout_strategies.*`,
+but it's not yet possible.
 
 Available layout strategies include:
   horizontal:
@@ -248,6 +249,24 @@ Available layout strategies include:
   flex:
   - See |layout_strategies.flex|
 
+Available tweaks to the settings in layout defaults include
+(can be applied to horizontal and vertical layouts):
+  mirror (default is `false`):
+  - Flip the view of the current layout:
+    - If using horizontal: if `true`, swaps the location of the
+      results/prompt window and preview window
+    - If using vertical: if `true`, swaps the location of the results and
+      prompt windows
+
+  width_padding:
+  - How many cells to pad the width of Telescope's layout window
+
+  height_padding:
+  - How many cells to pad the height of Telescope's layout window
+
+  preview_width:
+  - Change the width of Telescope's preview window
+
 
 layout_strategies.center()                        *layout_strategies.center()*