readme: cspell command

Signed-off-by: Ethan Perruzza <[email protected]>

README.md

@@ -41,6 +41,14 @@ docker run --rm -it \
 ./hugo.sh
 ```
 
+## Spell Checker
+
+```
+cspell --config cspell/cspell.json
+```
+
+If you need to use a specific word that isn't in the dictionaries, you can add it to the correct `.txt` dictionary in the `cspell` folder.
+
 ## Contributing
 
 If you think OSRD doesn't quite fit your needs yet, but still believe it could,
@@ -53,4 +61,4 @@ For more information on how to contribute, check out the [Contributing file](./C
 
 ## Get in touch
 
-Send an email at <[email protected]>, [open an issue](https://github.com/OpenRailAssociation/osrd-website/issues/new), or join the [#public-general:osrd.fr](https://matrix.to/#/#public-general:osrd.fr) matrix channel.
+Send an email at <[email protected]>, [open an issue](https://github.com/OpenRailAssociation/osrd-website/issues/new), or join the [#public-general:osrd.fr](https://matrix.to/#/#public-general:osrd.fr) matrix channel.