Improve showcase documentation

[Vladyslav-Kuksiuk]

This PR:

• improves the showcase documentation to make it clearer that the embed-code application is not tied to any specific source code language;
• adds a Quick Start guide with a minimal working configuration;
• updates the release workflow to package Linux binaries into archives, preserving their executable permissions.

Closes #109 as unnecessary.
Closes #110 as unnecessary.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.37%. Comparing base (62132b0) to head (e08c653).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #112   +/-   ##
=======================================
  Coverage   82.37%   82.37%           
=======================================
  Files          43       43           
  Lines        2951     2951           
=======================================
  Hits         2431     2431           
  Misses        390      390           
  Partials      130      130           

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