DOCS: API: add routing helper examples

Let's add an example usage of all of the routing helpers (visit,
currentRouteName, currentURL) to the API docs.

(cherry picked from commit fa068a0)

Author: Geodewd549

API.md

@@ -551,6 +551,20 @@ Navigate the application to the provided URL.
 *   `url` **[string][64]** The URL to visit (e.g. `/posts`)
 *   `options` **[object][72]** app boot options
 
+#### Examples
+
+Visiting the route for post 1.
+
+```javascript
+await visit('/posts/1');
+```
+
+Visiting the route for post 1 while also providing the `rootElement` app boot option.
+
+```javascript
+await visit('/', { rootElement: '#container' });
+```
+
 Returns **[Promise][66]\<void>** resolves when settled
 
 ### currentRouteName
@@ -1241,23 +1255,23 @@ Returns **([Array][70]\<Warning> | [Promise][66]<[Array][70]\<Warning>>)** An ar
 
 [54]: #getdeprecations
 
-[55]: #examples-22
+[55]: #examples-23
 
 [56]: #getdeprecationsduringcallback
 
 [57]: #parameters-29
 
-[58]: #examples-23
+[58]: #examples-24
 
 [59]: #getwarnings
 
-[60]: #examples-24
+[60]: #examples-25
 
 [61]: #getwarningsduringcallback
 
 [62]: #parameters-30
 
-[63]: #examples-25
+[63]: #examples-26
 
 [64]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
 

addon-test-support/@ember/test-helpers/setup-application-context.ts

@@ -130,6 +130,18 @@ export function setupRouterSettlednessTracking() {
   @param {string} url The URL to visit (e.g. `/posts`)
   @param {object} options app boot options
   @returns {Promise<void>} resolves when settled
+
+  @example
+  <caption>
+    Visiting the route for post 1.
+  </caption>
+  await visit('/posts/1');
+
+  @example
+  <caption>
+    Visiting the route for post 1 while also providing the `rootElement` app boot option.
+  </caption>
+  await visit('/', { rootElement: '#container' });
 */
 export function visit(
   url: string,