Add all new recipe filter keywords from 5 x new recipes

Author: sadielbartholomew

DOCUMENTATION.md

@@ -37,7 +37,7 @@
   ```
 
 * If the filter doesn't exist, it has to be added in `<div class="filter-menu">` 
-  alphabetically for `/docs/source/recipes/README.rst`, e.g.,
+  alphabetically for `docs/source/recipes/README.rst`, e.g.,
 
   ```html
   <div class="filter-menu">

docs/source/recipes/README.rst

@@ -55,6 +55,9 @@ Click on the keywords below to filter the recipes according to their function:
        <button data-filter="regrid">Regrid</button>
        <button data-filter="subspace">Subspace</button>
        <button data-filter="mask">Mask</button>
+       <button data-filter="vectorplot">Vectorplot</button>
+       <button data-filter="subplot">Subplot</button>
+       <button data-filter="stats">Statistical Operations</button>
    </div>
 
 .. raw:: html