docs: use includes for command help output

docs/commands/test-pairlist.md

@@ -0,0 +1,22 @@
+```
+usage: freqtrade test-pairlist [-h] [--userdir PATH] [-v] [-c PATH]
+                               [--quote QUOTE_CURRENCY [QUOTE_CURRENCY ...]]
+                               [-1] [--print-json] [--exchange EXCHANGE]
+
+options:
+  -h, --help            show this help message and exit
+  --userdir PATH, --user-data-dir PATH
+                        Path to userdata directory.
+  -v, --verbose         Verbose mode (-vv for more, -vvv to get all messages).
+  -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.
+  --quote QUOTE_CURRENCY [QUOTE_CURRENCY ...]
+                        Specify quote currency(-ies). Space-separated list.
+  -1, --one-column      Print output in one column.
+  --print-json          Print list of pairs or market symbols in JSON format.
+  --exchange EXCHANGE   Exchange name. Only valid if no config is provided.
+
+```