fix: allow custom base template to add params to feedback form

src/wuttaweb/templates/base.mako

@@ -526,16 +526,21 @@
                 })
             },
 
-            sendFeedback() {
-                this.sendingFeedback = true
-
-                const params = {
+            getParams() {
+                return {
                     referrer: this.referrer,
                     user_uuid: this.userUUID,
                     user_name: this.userName,
                     message: this.message.trim(),
+                    ...this.getExtraParams(),
                 }
+            },
 
+            getExtraParams() {},
+
+            sendFeedback() {
+                this.sendingFeedback = true
+                const params = this.getParams()
                 this.wuttaPOST(this.action, params, response => {
 
                     this.$buefy.toast.open({