chore: some small changes in the cypress README.md (#793)

Co-authored-by: Dominik Pschenitschni <mail@celement.de>
Reviewed-on: https://kolaente.dev/vikunja/frontend/pulls/793
Co-authored-by: dpschen <dpschen@noreply.kolaente.de>
Co-committed-by: dpschen <dpschen@noreply.kolaente.de>

cypress/README.md

@@ -22,20 +22,20 @@ It uses the same configuration as the CI.
 
 To use it, run
 
-```
+```shell
 docker-compose up -d
 ```
 
 Then, once all containers are started, run
 
-```
+```shell
 docker-compose run cypress bash
 ```
 
 to get a shell inside the cypress container.
 In that shell you can then execute the tests with
 
-```
+```shell
 yarn test:frontend
 ```
 
@@ -43,6 +43,6 @@ yarn test:frontend
 
 To open the Cypress Dashboard and run tests from there, run
 
-```
+```shell
 yarn cypress:open
 ```