update index.html

[InspiredGuy]

Issue #, if available:
n/a

Description of changes:
Removes link to https://htmlplayground.online/ since it gives 403. Updates logos for projects which had outdated logo urls. Small visual adjustments for couple of logos (placement, background). Check how it looks like at https://raw.githack.com/ajaxorg/ace/update-real-world-users/index.html#nav=production

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.79%. Comparing base (1bad1a1) to head (b4802ae).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5609   +/-   ##
=======================================
  Coverage   86.79%   86.79%           
=======================================
  Files         594      594           
  Lines       43129    43129           
  Branches     7149     7149           
=======================================
  Hits        37434    37434           
  Misses       5695     5695           

Flag	Coverage Δ
unittests	86.79% <ø> (ø)

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