doc: configure third-party extension table as longtable

The list of third-party extensions is larger than a given PDF page,
causing undesired rendering issues. Hint that the table should be built
with as a long-table to allow it to expand on multiple pages.

Signed-off-by: James Knight <[email protected]>

Author: jdknight

doc/features.rst

@@ -223,7 +223,7 @@ interacting with this extension:
 
     .. tabularcolumns:: |p{5cm}|p{11cm}|
 
-.. rst-class:: no-wrap-links
+.. rst-class:: longtable no-wrap-links
 
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 Type                              Notes