Make docs compliant with ansible recommended structure

docs/vars.md

@@ -0,0 +1,32 @@
+# Required variables
+These variables are required by some roles. Example values included.
+
+```
+timezone: 'Europe/Helsinki'
+domain: 'example.tld'
+email: 'admin@domain.tld'
+```
+
+# Default variables
+These variables have default values (shown below) which can be overridden.
+
+```
+install_packages:
+  - vim
+  - git
+  - etckeeper
+  - net-tools
+  - nmap
+  - ncdu
+  - fish
+  - parted
+```
+
+# Optional variables
+These variables are not required and not defined by default. Example values included.
+
+```
+delete_packages:
+  - nano
+  - curl
+```