Application to sign via digital certificate. Developed by the Spanish
government. Launchable by browsers to sign in webpages when
required.

Tested on Mozilla Firefox, Google Chrome and Microsoft Edge.

Notes:
  - The only UI language is Spanish, by now.
  - Forge at: https://github.com/ctt-gob-es/clienteafirma
  - If you download the package via wget, don't forget to set the
    -user-agent parameter.