test(table-of-contents): add e2e-storybook test coverage (#7673)

### Related Ticket(s)

Closes: #7444 #7445 #7446 

### Description

- Adds new e2e-storybook test for table-of-contents web components component
- Adds new e2e-storybook test for table-of-contents react component
- Adds new cypress-local.json config & yarn commands to make test writing & debugging easier

### Changelog

**New**

- Adds new command `yarn test:e2e-storybook:dev` that opens the Cypress client on a currently-running storybook instance to ease test writing & debugging
- Adds e2e-storybook test coverage for `table of contents` component

packages/react/package.json

@@ -41,6 +41,7 @@
     "test:e2e:test:no-percy": "start-server-and-test 'yarn test:e2e:run' 8080 'cypress run --config video=false --config-file tests/e2e/cypress.json'",
     "test:e2e-storybook:run": "http-server -c-1 storybook-static --silent -p 8082",
     "test:e2e-storybook:test": "start-server-and-test 'yarn test:e2e-storybook:run' 8082 'percy exec --config tests/e2e-storybook/.percy.json -- cypress run --config video=false --config-file tests/e2e-storybook/cypress.json'",
+    "test:e2e-storybook:dev": "cypress open --config-file ./tests/e2e-storybook/cypress-local.json",
     "test:e2e-storybook:test:no-percy": "start-server-and-test 'yarn test:e2e-storybook:run' 8082 'cypress run --config video=false --config-file tests/e2e-storybook/cypress.json'",
     "test:e2e-storybook:test:no-percy:with-video": "start-server-and-test 'yarn test:e2e-storybook:run' 8082 'cypress run --config-file tests/e2e-storybook/cypress.json'",
     "test:e2e-storybook:browserstack:canary": "browserstack-cypress run --cf tests/e2e-storybook/browserstack.json --ccf tests/e2e-storybook/cypress-canary.json --sync",

packages/react/tests/e2e-storybook/cypress-local.json

@@ -0,0 +1,17 @@
+{
+  "baseUrl": "http://localhost:9000",
+  "browser": "chrome",
+  "headless": true,
+  "fixturesFolder": "tests/e2e-storybook/cypress/fixtures",
+  "fileServerFolder": "storybook-static",
+  "screenshotsFolder": "tests/e2e-storybook/cypress/screenshots",
+  "videosFolder": "tests/e2e-storybook/cypress/videos",
+  "integrationFolder": "tests/e2e-storybook/cypress/integration",
+  "supportFile": "tests/e2e-storybook/cypress/support/index.js",
+  "pluginsFile": "tests/e2e-storybook/cypress/plugins/index.js",
+  "nodeVersion": "system",
+  "includeShadowDom": true,
+  "testFiles": "**/*.e2e.js",
+  "pageLoadTimeout": 40000,
+  "defaultCommandTimeout": 40000
+}