Add event delegation for form tracking

- Global event listeners are now used instead of per-element listeners
- Event listeners now use the capture phase instead of bubble
- Forms added after the initial `enableFormTracking` call should
  automatically be tracked without needing additional calls
- Field value transform functions can now return `null` for all events
- Add unit tests for form tracking
- The new `targets` parameter allows listening for forms in only a
  subset of the document tree, or across multiple same-origin documents
  (e.g. iframes)

Author: jethron

common/changes/@snowplow/browser-plugin-form-tracking/PE-6528-formsv4_2024-07-17-01-15.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@snowplow/browser-plugin-form-tracking",
+      "comment": "Add event delegation for link click tracking",
+      "type": "none"
+    }
+  ],
+  "packageName": "@snowplow/browser-plugin-form-tracking"
+}

common/changes/@snowplow/javascript-tracker/PE-6528-formsv4_2024-07-17-01-15.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@snowplow/javascript-tracker",
+      "comment": "",
+      "type": "none"
+    }
+  ],
+  "packageName": "@snowplow/javascript-tracker"
+}

plugins/browser-plugin-form-tracking/jest.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  preset: 'ts-jest',
+  reporters: ['jest-standard-reporter'],
+  setupFilesAfterEnv: ['../../setupTestGlobals.ts'],
+  testEnvironment: 'jest-environment-jsdom-global',
+};

plugins/browser-plugin-form-tracking/package.json

@@ -19,7 +19,7 @@
   ],
   "scripts": {
     "build": "rollup -c --silent --failAfterWarnings",
-    "test": ""
+    "test": "jest"
   },
   "dependencies": {
     "@snowplow/browser-tracker-core": "workspace:*",