Deduplicating docs with har.fyi

[max-ostapenko]

I started working on query migration guide, and found that this repo and har.fyi have a few duplicated docs. As har.fyi is a bit better looking than Github files, here is an idea to improve this a bit.

Move to har.fyi:

• [x] docs/guided_tour.md
• [x] docs/gettingstarted_bigquery.md
• [x] docs/guided_tour_summary_pages.md
• [x] docs/guided_tour_summary_requests.md
• [x] docs/guided_tour_summary_pages_requests.md

I think it may be useful to keep the version of the guide here while multiple types of tables are maintained.

Maintenance and visitor docs that make sense to keep in this repo as dev documentation:

• docs/reports.md
• docs/faq.md
• docs/cwv_tech_report.md

This should make it a bit more straightforward for new analysts, make maintenance easier.

P.S> If there are any other docs to take into consideration, please comment.

[max-ostapenko]

@rviscomi sorry, still not ready. Wanted to break it into 2 PRs:

• deduplication
• migration to all

but too many interdependencies.

[max-ostapenko]

@rviscomi now ready. You may find guides overview page in this PR.