ajson: add page (#4191)

pages/common/ajson.md

@@ -0,0 +1,20 @@
+# ajson
+
+> Executes JSONPath on JSON objects.
+> More information: <https://github.com/spyzhov/ajson>.
+
+- Read JSON from a file and execute a specified JSONPath expression:
+
+`ajson '{{$..json[?(@.path)]}}' {{path/to/file.json}}`
+
+- Read JSON from stdin and execute a specified JSONPath expression:
+
+`cat {{path/to/file.json}} | ajson '{{$..json[?(@.path)]}}'`
+
+- Read JSON from a URL and evaluate a specified JSONPath expression:
+
+`ajson '{{avg($..price)}}' '{{https://example.com/api/}}'`
+
+- Read some simple JSON and calculate a value:
+
+`echo '{{3}}' | ajson '{{2 * pi * $}}'`