Add option to provide custom SSL certificates during development

[woochica]

The webpack-dev-server can be configured to use custom SSL certificates. Change the default config to look for enviroment variables SSL_CRT_FILE and SSL_KEY_FILE and set them if they exist when using HTTPS.

This change was inspired by create-react-app: https://create-react-app.dev/docs/using-https-in-development/#custom-ssl-certificate https://github.com/facebook/create-react-app/commit/0299c0e6e70bca24da7a59eb5adbd4a2374a309c