Update docs for linting and modifying configs

README.md

@@ -37,3 +37,16 @@ git push origin v3.1
 ```
 
 The CI jobs will then build your release and make it available at `https://github.com/panda-re/linux_builder/releases/download/<TAG-NAME>/kernels-latest.tar.gz`
+
+## Modifying configs
+If you'd like to add a given option or set of options to all configs, you can do something like:
+
+```sh
+# write your configs into delta.txt
+for f in $(cat delta.txt); do for t in $(ls config.*); do  echo $f>>$t; done; done
+# Run linter as shown below
+git commit -a
+```
+
+## Linting configs
+Before commiting any config update you MUST lint your change by running `./build.sh configonly`. You can specify architectures to lint by listing them as additional arguments, e.g., `./build.sh configonly armel mipel`.