mark idea as done in readme

README.md

@@ -10,12 +10,12 @@
 
 ## Brrr Ideas to Implement
 
-- [ ] [Subresource Integrity](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity)
+- [x] [Subresource Integrity](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity)
 
 ## License
 
 Source codes are licensed under [GPL3](./LICENSE).
 
 Contents of this blog, including but not limited to articles/posts, pictures,
 illustrations and audio etc., are licensed under [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/)
-if not explicitly declared otherwise.
+if not explicitly declared otherwise.