docs: update Drone CI integration

[reddec]

Updates Drone CI integration, which includes:

• simplified and deterministic usage of go-releaser (ie: docker image)
• shows how to build docker images in Drone docker pipeline

[codecov]

Codecov Report

Merging #2789 (b354fe2) into main (3a04e75) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #2789   +/-   ##
=======================================
  Coverage   84.95%   84.95%           
=======================================
  Files         106      106           
  Lines        8241     8241           
=======================================
  Hits         7001     7001           
  Misses       1010     1010           
  Partials      230      230           

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[caarlos0]

Thanks!