DOC: Prepare release notes for 3.7.0

DOC: updated the supported versions of Matplotlib

DOC: re-run the github status

DOC: start to merge the whats_new

DOC: re-arrange whats new

DOC: add top-level rst TOC for 3.7 docs

DOC: fix markup in github stats

3.7.0 behavior and deprecation release notes

3.7.0 removals

DOC: merge up development API changes

DOC: spell behaviour britishly

Remove files, add last release note

DOC: update switcher.json

Fix broken links

DOC: fix internal links

DOC: more links

fix version number in dependency version list

Last couple release notes

Update github stats

Author: tacaswell

SECURITY.md

@@ -1,14 +1,19 @@
 [
     {
-        "name": "3.6 (stable)",
+        "name": "3.7 (stable)",
         "version": "stable",
         "url": "https://matplotlib.org/stable/"
     },
     {
-        "name": "3.7 (dev)",
+        "name": "3.8 (dev)",
         "version": "dev",
         "url": "https://matplotlib.org/devdocs/"
     },
+    {
+        "name": "3.6",
+        "version": "3.6.3",
+        "url": "https://matplotlib.org/3.6.3/"
+    },
     {
         "name": "3.5",
         "version": "3.5.3",