Added support for adding objects

pkg/yqlib/doc/operators/headers/add.md

@@ -4,7 +4,7 @@ Add behaves differently according to the type of the LHS:
 * arrays: concatenate
 * number scalars: arithmetic addition
 * string scalars: concatenate
+* maps: shallow merge (use the multiply operator (`*`) to deeply merge)
 
-Use `+=` as append assign for things like increment. Note that `.a += .x` is equivalent to running `.a = .a + .x`.
+Use `+=` as a relative append assign for things like increment. Note that `.a += .x` is equivalent to running `.a = .a + .x`.
 
-Add is not (yet) supported for maps - however you can use merge `*` which will have a similar effect...