Add system diagram using mermaid markdown

[yurishkuro]

Cool new feature on GitHub https://github.blog/2022-02-14-include-diagrams-markdown-files-mermaid/

Interactive editor: https://mermaid-js.github.io/mermaid-live-editor/edit

[yurishkuro]

cc @joe-elliott @albertteoh @pavolloffay

[codecov]

Codecov Report

Merging #3529 (4f6126f) into main (aa4c2e6) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3529      +/-   ##
==========================================
+ Coverage   96.44%   96.48%   +0.03%     
==========================================
  Files         263      263              
  Lines       15376    15376              
==========================================
+ Hits        14830    14836       +6     
+ Misses        461      456       -5     
+ Partials       85       84       -1     

Impacted Files	Coverage Δ
cmd/query/app/static_handler.go	95.80% <0.00%> (+1.79%)	⬆️
pkg/config/tlscfg/cert_watcher.go	94.73% <0.00%> (+2.10%)	⬆️
cmd/collector/app/server/zipkin.go	70.73% <0.00%> (+2.43%)	⬆️

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[frzifus]

like it :) However, in dark mode the README.md file looks a bit like a big black hole.

[albertteoh]

👍🏼 Very cool!