Add docs for label translation

docs/development/forms.md

@@ -0,0 +1,31 @@
+# Forms
+
+## Translations
+
+The label for a field will be automatically translated. 
+
+```php
+    ...
+        ->add(
+            'username',
+            TextType::class,
+        )
+    ...
+```
+
+Will result in
+
+```html
+
+<div class="form-group">
+  <label for="xxx_form_username" class="form-label">
+    Username<abbr title="this field is required">*</abbr>
+  </label>
+  <input type="text" id="xxx_form_username" name="xxx_form[username]" required="required" class="form-control">
+</div>
+```
+Where `Username` is a translation. So if you want to translate the label, you can do it like this:
+
+```yaml
+Username: 'Enter your username'
+```