track additional browse events in posthog

[gumaerc]

What are the relevant tickets?

Closes https://github.com/mitodl/hq/issues/6624

Description (What does it do?)

This PR corrects some Posthog tracking behavior in relation to the "browse" workflow on the site, more specifically regarding topics / subtopics / related topics.

How can this be tested?

• Make sure you have Posthog configured and pointing at your own custom project
• Open a tab with your Posthog activity dashboard
• Open another tab and visit the homepage at http://localhost:8062/
• Click the "Topic" link in "or browse by Topic" below the home page search
• Check your Posthog activity and verify that you see a clicked_hero_browse_topics event
• Return to the homepage and scroll down to the "Browse by Topic" section
• Click one of the topic buttons
• Check Posthog and verify you see a topic_clicked event
• Return to the homepage and scroll back down to the "Browse by Topic" section again
• Click the "See All" link
• Check Posthog and verify that you see a home_see_all_topics_clicked event
• Now on the topics listing page, click a top level topic
• Check Posthog and verify that you see a topic_clicked event
• Return back to the topics listing page and click one of the subtopic pills
• Check Posthog and verify that you see a subtopic_clicked event
• Return back to the topics listing page and click one of the top level topics
• On the topic channel page, you should see a "Subtopics" section, click one
• Check Posthog and verify that you see a subtopic_clicked event
• On the subtopic channel page, you should see a "Related Topics" section, click one
• Check Posthog and verify that you see a related_topic_clicked event

[shanbady]

something to consider - we have a bunch of these bare event strings. it might be good to have them defined as constants somewhere so its easier to track and change

[shanbady]

worked when i tested it. received all the events. left minor non-blocking suggestion