Typo: Correction from "RT diagrams" to "ER diagrams" in README

[huhh-myan]

In the Section What You'll Learn section of the README,
"Data Modeling" bullet currently says :

Data modeling: How to develop entities, relationships and RT diagrams to represent data requirements visually.

I think RT diagrams should be changed to ER diagrams.

Suggested Correction:

Data modeling: How to develop entities, relationships and ER diagrams to represent data requirements visually.