chore(gno.land): add playground section, add GopherconUS to events page

[leohhhn]

Description

As the title says, on request by @ilgooz & marketing. Shadows #1641.

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.43%. Comparing base (ce47828) to head (ce939a4).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1741   +/-   ##
=======================================
  Coverage   47.43%   47.43%           
=======================================
  Files         384      384           
  Lines       61201    61201           
=======================================
  Hits        29028    29028           
  Misses      29744    29744           
  Partials     2429     2429           

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