Improve README (#214)

Author: EpocDotFr

README.md

@@ -68,9 +68,11 @@ Dependencies
 1. Retrieve the dependencies:
 
     ```
-    composer install
+    composer install --no-dev
     ```
 
+    Remove `--no-dev` if you plan to install Davis locally for e.g. development purposes.
+
 2. At least put the correct credentials to your database (driver and url) in your `.env.local` file so you can easily create the necessary tables.
 
 3. Run the migrations to create all the necessary tables:
@@ -93,6 +95,10 @@ Create your own `.env.local` file to change the necessary variables, if you plan
 >
 > If your installation is behind a web server like Apache or Nginx, you can setup the env vars directly in your Apache or Nginx configuration (see below). Skip this part in this case.
 
+> [!CAUTION]
+>
+> In a production environnement, the `APP_ENV` variable MUST be set to `prod` to prevent leaking sensitive data.
+
 **a. The database driver and url** (_you should already have it configured since you created the database previously_)
     
 ```shell