docs: Update README.md (#220)

Add number of contributors

Author: ashishb

README.md

@@ -6,6 +6,7 @@
 [![Lint Markdown](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-markdown.yaml/badge.svg)](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-markdown.yaml)
 [![Lint YAML](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-yaml.yaml/badge.svg)](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-yaml.yaml)
 [![Lint GitHub Actions](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-github-actions.yaml/badge.svg)](https://github.com/ashishb/android-security-awesome/actions/workflows/lint-github-actions.yaml)
+![GitHub contributors](https://img.shields.io/github/contributors/ashishb/android-security-awesome)
 
 A collection of Android security-related resources.