Some documentary information.

README.md

@@ -2,6 +2,26 @@
 
 See <https://github.com/h5bp/lazyweb-requests/issues/150>.
 
+# Contribute
+
+If you want to add a badge, only modify `badges.json`.
+
+The format is the following:
+
+```js
+/* Unique name of your badge. */
+"build-passed": {
+  /* Textual information shown, in order. */
+  "text": [ "build", "passed" ],
+  /* Width of the first box, width of the second box. */
+  "widths": [ 33, 44 ],
+  /* Gradient of the background color of the second box.
+   * The main gradient is from index 1 to 2,
+   * indices 0 and 4 provide the light and dark outline. */
+  "colorB": [ "#8f6", "#4c1", "#3b0", "#370" ]
+}
+```
+
 # License
 
 All work here is licensed CC0.