Add documentation for the Outline pane (#327)

* Add documentation and images for the outline pane
* Use literal formatting for special comments in Outline pane
* Tweak crop and compress Options menu image for Outline pane
* Clean up line breaks & spaces in Outline pane
* Apply/fix reST formatting and capitalize Outline/outline consistently
* Use consistent tense in options menu item list in Outline pane
* Add reviewer feedback

Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>
Co-authored-by: Stephannie Jimenez Gacha <steff456@users.noreply.github.com>

doc/panes/outline.rst

@@ -0,0 +1,58 @@
+#######
+Outline
+#######
+
+The **Outline** pane allows you to view and navigate the functions, classes, methods, cells and comments in open Python files.
+To show or hide the Outline pane, use :menuselection:`View --> Panes --> Outline` or :kbd:`Ctrl-Shift-O` / :kbd:`Cmd-Shift-O`.
+Click an entry in the outline to jump to its source file location, and use the :guilabel:`Go to cursor position` toolbar button to highlight the item corresponding to the current :doc:`editor` position.
+
+.. image:: /images/outline/outline-standard.png
+   :alt: Outline pane
+
+
+
+============
+Options menu
+============
+
+The options menu in the top-right of the pane allows customizing how the outline is displayed.
+
+.. image:: /images/outline/outline-options-menu.png
+   :alt: Outline options menu
+
+These customization settings include:
+
+* :guilabel:`Show absolute path`: Display the full path to each file instead of just the name.
+* :guilabel:`Show all files`: List every open file rather than just the current one.
+  This allows using the Outline as a file switcher.
+* :guilabel:`Group code cells`: Group code cells in multiple nested levels in the outline rather than showing all cells in one level.
+  You can create subsections by adding more ``%`` signs to the cell separator.
+* :guilabel:`Display variables and attributes`: Display top-level variable/constant definitions and class attributes in the outline.
+* :guilabel:`Follow cursor position`: Automatically highlight and expand the entry corresponding to the current cursor position in the :doc:`editor`.
+* :guilabel:`Show special comments`: List special comments in the outline, which start with ``# ----``.
+* :guilabel:`Sort files alphabetically`: Sort the file list in alphabetical order.
+  When disabled, all tabs will be sorted by the tab order of the currently selected Editor panel.
+
+
+
+=====
+Icons
+=====
+
+The following icons are used for outline elements:
+
+* :guilabel:`m` for methods
+* :guilabel:`f` for functions
+* :guilabel:`c` for classes
+* :guilabel:`%` for code cells
+* :guilabel:`#` for comments
+
+
+
+=============
+Related panes
+=============
+
+* :doc:`editor`
+* :doc:`fileexplorer`
+* :doc:`projects`