Update tutorial on adding new extensions

CHANGELOG.md

@@ -11,6 +11,7 @@
 ### Fixed
 
 - Self links no longer included in Items for "relative published" catalogs ([#725](https://github.com/stac-utils/pystac/pull/725))
+- Adding New and Custom Extensions tutorial now up-to-date with new extensions API ([#724](https://github.com/stac-utils/pystac/pull/724))
 
 ### Deprecated
 

docs/tutorials.rst

@@ -55,4 +55,8 @@ implement your own custom extensions.
     :maxdepth: 2
     :glob:
 
-    tutorials/**
+    tutorials/pystac-introduction.ipynb
+    tutorials/pystac-spacenet-tutorial.ipynb
+    tutorials/how-to-create-stac-catalogs.ipynb
+    tutorials/creating-a-landsat-stac.ipynb
+    tutorials/adding-new-and-custom-extensions.ipynb