Add poetry command to readme

README.rst

@@ -46,6 +46,7 @@ Usage
         --encoding <charset>  Use encoding parameter for file open
         --savepath <file>     Save the list of requirements in the given file
         --print               Output the list of requirements in the standard output
+        --poetry              Run poetry to add all requirements to pyproject.toml file
         --force               Overwrite existing requirements.txt
         --diff <file>         Compare modules in requirements.txt to project imports.
         --clean <file>        Clean up requirements.txt by removing modules that are not imported in project.