Reorganize directories (#3462)

* 🚚 move files
* 🚚 rename doc folder to docs
* 🚚 rename test folder to tests

docs/examples/operator_serialize.output

@@ -0,0 +1,22 @@
+{"one":1,"two":2}
+
+[1,2,4,8,16]
+
+{
+    "one": 1,
+    "two": 2
+}
+
+[
+  1,
+  2,
+  4,
+  8,
+  16
+]
+
+{
+	"one": 1,
+	"two": 2
+}
+