Add property to feedback widget to capture page location.

[antfitch]

Description of what this PR is changing or adding, and why:

We want developers to be able to rate our pages. We can do this now, but we're not capturing the page location that they want to rate. Added an additional parameter to our event tag to capture this.

@RedBrogdon are you able to take a quick look?

Issues fixed by this PR (if any):

PRs or commits this PR depends on (if any):

Presubmit checklist

• This PR is marked as draft with an explanation if not meant to land until a future stable release.
• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 3584a2d):

https://flutter-docs-prod--pr11837-analytics-add-properties-knkib2nw.web.app

[antfitch]

Never mind. I don't think we need this field.

[antfitch]

Actually, I think we might need this. Can someone review?