add gc-test plugin (#597)

plugins/wasm-go/extensions/gc-test/README.md

@@ -0,0 +1,28 @@
+---
+title: GC Test
+keywords: [higress, gc test]
+description: use to test the gc of tinygo
+---
+
+## Description
+
+The `gc-test` plugin is used to test whether there are memory leaks in TinyGO's GC mechanism.
+
+This plugin should not be used in production.
+
+## Configuration Fields
+
+| Name        | Type            | Requirement | Default Value | Description                                          |
+| ----------- | --------------- | --------    | ------        | ---------------------------------------------------- |
+| `bytes`     | Number          | Required    | -             | Number of bytes allocated per-request                |
+
+
+## How to
+
+The plugin will response the stats of memory as follows:
+
+```bash
+{"Sys": 15073280,"HeapSys": 10682368,"HeapIdle": 139264,"HeapInuse": 0,"HeapReleased": 0}
+```
+
+We can use bench tools to test whether the `HeapSys` field keeps growing, and then we can determine whether a memory leak has occurred.