docs(reporting): add usage into README.md

Author: MikaelVallenet

reporting/README.md

@@ -5,4 +5,23 @@ For launching the reporting script, you will need a github & twitter token.
 
 You can find these tokens in the following links:
 - twitter: https://developer.twitter.com/en/docs/authentication/oauth-2-0
-- github: https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token
+- github: https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/creating-a-personal-access-token
+
+## Usage
+
+```bash
+USAGE
+  reporting [flags]
+
+FLAGS
+  -backlog=true           generate backlog
+  -changelog=true         generate changelog
+  -curation=true          generate curation
+  -format markdown        output format
+  -github-token ...       github token
+  -help=false             show help
+  -output-path ./output/  output directory path
+  -since ...              since date RFC 3339 (ex: 2003-01-19T00:00:00.000Z)
+  -tips=true              generate tips
+  -twitter-token ...      twitter token
+```