README: Add OpenSSF badge (#242)

README.md

@@ -5,6 +5,7 @@
 [![Super-Linter](https://github.com/nietras/Sep/actions/workflows/super-linter.yml/badge.svg)](https://github.com/marketplace/actions/super-linter)
 [![codecov](https://codecov.io/gh/nietras/Sep/branch/main/graph/badge.svg?token=WN56CR3X0D)](https://codecov.io/gh/nietras/Sep)
 [![CodeQL](https://github.com/nietras/Sep/workflows/CodeQL/badge.svg)](https://github.com/nietras/Sep/actions?query=workflow%3ACodeQL)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/9962/badge)](https://www.bestpractices.dev/projects/9962)
 [![Nuget](https://img.shields.io/nuget/v/Sep?color=purple)](https://www.nuget.org/packages/Sep/)
 [![Release](https://img.shields.io/github/v/release/nietras/Sep)](https://github.com/nietras/Sep/releases/)
 [![downloads](https://img.shields.io/nuget/dt/Sep)](https://www.nuget.org/packages/Sep)