* set color to `.form-control-plaintext`
* fixes readability on dark themes like ‘darkly’
  * https://bootswatch.com/darkly/index.html#forms
  * https://bootswatch.com/slate/index.html#forms
  * https://bootswatch.com/superhero/index.html#superhero
  * https://bootswatch.com/solar/index.html#forms

/cc @thomaspark