feat(docs): adds BugHerd to documentation site.

[rusackas]

SUMMARY

Adds BugHerd to the Superset (docs) website. This will better allow all visitors to point out errors and omissions in the documentation site, if they're not able or willing to open a pull request themselves.

BugHerd has been kind enough to give us a free account on their service for this purpose, with enough seats to invite Superset committers and/or PMC members to help moderate and implement these requests.

This in turn brings up an interface to allow submission of feedback:

Any anonymous user can add their feedback that (optionally) is left on a particular DOM element:

That lands in the "Feedback" backlog:

Which can be triaged to the kanban board (or discarded)

The tasks then show the admin user exactly where on the page the note was left, and provides various means for commenting/follow-up

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #23287 (0cc72eb) into master (d16512b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #23287   +/-   ##
=======================================
  Coverage   67.36%   67.36%           
=======================================
  Files        1909     1909           
  Lines       73488    73488           
  Branches     7987     7987           
=======================================
  Hits        49504    49504           
  Misses      21934    21934           
  Partials     2050     2050           

Flag	Coverage Δ
javascript	53.78% <ø> (ø)
mysql	78.44% <ø> (ø)
postgres	78.50% <ø> (ø)
python	81.92% <ø> (ø)
unit	52.49% <ø> (ø)

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[dpgaspar]

Uau, this is awesome!