Show query in user search header

[Torgen]

Also close dropdown on enter, and allow clearing search without reopening dropdown.

Fixes #1316

[github-actions]

Bundle size diff:

Format	Base	Head	Diff
Minified	1025206	1025943	+737
Gzipped	272692	272787	+95
CSS	172933	173141	+208

Meteor Package size diff:

Package	Base	Head	Diff
app/app.js	377514	378251	+737

No change in top-level node module sizes.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.49%. Comparing base (967bfe3) to head (12689c4).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
client/blackboard.js	75.00%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1329      +/-   ##
==========================================
+ Coverage   82.27%   82.49%   +0.21%     
==========================================
  Files         114      114              
  Lines        7194     7202       +8     
  Branches     1350     1350              
==========================================
+ Hits         5919     5941      +22     
+ Misses        921      910      -11     
+ Partials      354      351       -3     

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