Only lowercase for email

src/app/signup/student-signup/student-signup.component.html

@@ -25,7 +25,7 @@
 
     <!-- Email -->
     <mat-form-field class="full-width">
-      <input matInput type="email" formControlName="email" placeholder="Adresse email" required>
+      <input matInput type="email" formControlName="email" placeholder="Adresse email" onkeyup="this.value = this.value.toLowerCase();" required>
       <mat-hint>
         Elle te servira d'identifiant de connexion.
       </mat-hint>