docs: use includes for command help output

docs/commands/new-config.md

@@ -0,0 +1,12 @@
+```
+usage: freqtrade new-config [-h] [-c PATH]
+
+options:
+  -h, --help            show this help message and exit
+  -c PATH, --config PATH
+                        Specify configuration file (default:
+                        `userdir/config.json` or `config.json` whichever
+                        exists). Multiple --config options may be used. Can be
+                        set to `-` to read config from stdin.
+
+```