doc: add blacklist plugin to plugin README.md
@@ -216,6 +216,7 @@ copied by the `spec` plugin just before) to validate values:
- [network](network/) by using network APIs
- [path](path/) by checking files on file system
- [unit](unit/) validates and normalizes units of memory (e.g. 20KB to 20000 Bytes)
+- [blacklist](blacklist/) blacklist and reject values
The same but experimental:
