README - Add EPA link to Shiny

**Is your feature request related to a problem? Please describe.**
Update README to include EPA link for Shiny app

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Also check with NALMS link
