Update README.md to include new features that have been added to secureli

[JordoHeffernan]

As a user I want documentation to be good

AC

1. Update info regarding PII Scan
   a. Feature/secureli-435: Implement custom PII scan #496
   b. Increase security scan to check for PII #435
2. Update info regarding language scanner
   a. Feature/secureli 436 language detection #481
   b. Change language detection on commit to only run against committed code #436
3. Update info regarding existing pre-commit-config
   a. feat: Use custom pre-commit config file #411
   b. Support preexisting hooks in .pre-commit-config.yaml #373
4. kotlin support
   a. feat: #392 kotlin language linter support #444
   b. Add linting support for Kotlin #392