Markdown section on DRY principles

[alaws-USGS]

• [ ] Create new Markdown and talk about writing code once and reusing in other parts (DRY programming = Don't Repeat Yourself). A good reference https://www.geeksforgeeks.org/dont-repeat-yourselfdry-in-software-development/
• [ ] Give the example that several components below (Time End, Time Start, etc) could likely be used multiple times between different charts