Add aria label to purpose form

src/registrar/forms/domain_request_wizard.py

@@ -524,7 +524,9 @@ class DotGovDomainForm(RegistrarForm):
 class PurposeForm(RegistrarForm):
     purpose = forms.CharField(
         label="Purpose",
-        widget=forms.Textarea(),
+        widget=forms.Textarea(attrs={
+            'aria-label': 'What is the purpose of your requested domain? Describe how you’ll use your .gov domain. Will it be used for a website, email, or something else? You can enter up to 2000 characters.'
+        }),
         validators=[
             MaxLengthValidator(
                 2000,