Huge improvements for docs (#58)

docs/content/doc/practical-instructions/new-config-options.md

@@ -0,0 +1,31 @@
+---
+date: "2019-02-12:00:00+02:00"
+title: "Adding new   config options"
+draft: false
+type: "doc"
+menu:
+  sidebar:
+    parent: "practical instructions"
+---
+
+# Adding new config options
+
+Vikunja uses [viper](https://github.com/spf13/viper) to handle configuration options.
+It handles parsing all different configuration sources.
+
+The configuration is done in sections. These are represented with a `.` in viper.
+Take a look at `pkg/config/config.go` to understand how these are set.
+
+To add a new config option, you should add a default value to `pkg/config/config.go`.
+Default values should always enable the feature to work somehow, or turn it off completely if it always needs
+additional configuration.
+
+Make sure to add the new config option to [the config document]({{< ref "../setup/config.md">}}) and the default config file
+(`config.yml.sample` at the root of the repository) to make sure it is well documented.
+
+If you're using a computed value as a default, make sure to update the sample config file and debian
+post-install scripts to reflect that.
+
+To get a configured option, use `viper.Get("config.option")`.
+Take a look at [viper's documentation](https://github.com/spf13/viper#getting-values-from-viper) to learn of the 
+different ways available to get config options.