feat: add ivy-style layout strategy (#771)

* feat: add new layout strategy

* [docgen] Update doc/telescope.txt
skip-checks: true

Co-authored-by: Github Actions <actions@github>

doc/telescope.txt

@@ -91,6 +91,37 @@ telescope.extensions()                                *telescope.extensions()*
 
 
 
+================================================================================
+                                                              *telescope.themes*
+
+Themes are ways to combine several elements of styling together.
+
+They are helpful for managing the several differnt UI aspects for telescope and
+provide a simple interface for users to get a particular "style" of picker.
+
+themes.get_dropdown()                                  *themes.get_dropdown()*
+    Dropdown style theme.
+
+    Usage:
+
+        `local builtin = require('telescope.builtin')`
+        `local themes = require('telescope.themes')`
+        `builtin.find_files(themes.get_dropdown())`
+
+
+
+themes.get_ivy()                                            *themes.get_ivy()*
+    Ivy style theme.
+
+    Usage:
+
+        `local builtin = require('telescope.builtin')`
+        `local themes = require('telescope.themes')`
+        `builtin.find_files(themes.get_ivy())`
+
+
+
+
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                                                          *telescope.actions.set*