docs: Move quick overview one level up (#2890)

* docs: Move quick overview one level up

* More text on attributes.

* minor text updates.

* Mention open,save_mfdataset

* Add some dataset text.

* Link to other sections in docs.

* minor edits.

* shoyer edits

Author: dcherian

doc/examples.rst

@@ -4,7 +4,6 @@ Examples
 .. toctree::
     :maxdepth: 2
 
-    examples/quick-overview
     examples/weather-data
     examples/monthly-means
     examples/multidimensional-coords

doc/examples/quick-overview.rst

@@ -29,6 +29,7 @@ Documentation
 
 * :doc:`why-xarray`
 * :doc:`faq`
+* :doc:`quick-overview`
 * :doc:`examples`
 * :doc:`installing`
 
@@ -39,6 +40,7 @@ Documentation
 
    why-xarray
    faq
+   quick-overview
    examples
    installing