fix: mark cli.py as non-executable (fixes #1590) (#1610)

* mark cli.py as non-executable
* add comments indicating the file should not be run directly

Author: xiongnemo

cve_bin_tool/cli.py

@@ -2,6 +2,14 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 
+# This file is not meant to be run directly.
+# It should be properly installed so the checkers will load correctly.
+# Refer to:
+#       manual (https://cve-bin-tool.readthedocs.io/en/latest/MANUAL.html)
+#       on how to use the tool, or
+#       installation guide (https://cve-bin-tool.readthedocs.io/en/latest/README.html#installing-cve-binary-tool)
+#       on how to install the tool.
+
 """
 This tool scans for a number of common, vulnerable open source components
 (openssl, libpng, libxml2, expat and a few others) to let you know if your