use default border color to support light theme

[jesseduffield]

No description provided.

[codecov-io]

Codecov Report

Merging #79 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #79   +/-   ##
=======================================
  Coverage   23.61%   23.61%           
=======================================
  Files          13       13           
  Lines        1080     1080           
=======================================
  Hits          255      255           
  Misses        813      813           
  Partials       12       12

Impacted Files	Coverage Δ
pkg/config/app_config.go	77.19% <100%> (ø)	⬆️

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