plot-profit: Make "auto-open" HTML result optional

Adding an "--auto-open" argument.
This improves tool processing of the results, while still allowing to open the HTML file for easy use.

freqtrade/commands/cli_options.py

@@ -433,6 +433,11 @@ AVAILABLE_CLI_OPTIONS = {
         metavar='INT',
         default=750,
     ),
+    "plot_auto_open": Arg(
+        '--auto-open',
+        help='Automatically open generated plot.',
+        action='store_true',
+    ),
     "no_trades": Arg(
         '--no-trades',
         help='Skip using trades from backtesting file and DB.',