README.md: add OpenSSF best practices badge

Lima is now passing the OpenSSF best practices badge:
https://www.bestpractices.dev/en/projects/6505

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

README.md

@@ -9,6 +9,8 @@
 
 # Lima: Linux Machines
 
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/6505/badge)](https://www.bestpractices.dev/projects/6505)
+
 [Lima](https://lima-vm.io/) launches Linux virtual machines with automatic file sharing and port forwarding (similar to WSL2).
 
 The original goal of Lima was to promote [containerd](https://containerd.io) including [nerdctl (contaiNERD ctl)](https://github.com/containerd/nerdctl)