docs: use includes for command help output

docs/commands/list-exchanges.md

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+```
+usage: freqtrade list-exchanges [-h] [-v] [--no-color] [--logfile FILE] [-V]
+                                [-c PATH] [-d PATH] [--userdir PATH] [-1] [-a]
+
+options:
+  -h, --help            show this help message and exit
+  -1, --one-column      Print output in one column.
+  -a, --all             Print all exchanges known to the ccxt library.
+
+Common arguments:
+  -v, --verbose         Verbose mode (-vv for more, -vvv to get all messages).
+  --no-color            Disable colorization of hyperopt results. May be
+                        useful if you are redirecting output to a file.
+  --logfile FILE, --log-file FILE
+                        Log to the file specified. Special values are:
+                        'syslog', 'journald'. See the documentation for more
+                        details.
+  -V, --version         show program's version number 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.
+  -d PATH, --datadir PATH, --data-dir PATH
+                        Path to directory with historical backtesting data.
+  --userdir PATH, --user-data-dir PATH
+                        Path to userdata directory.
+
+```