update `README.Rmd`

[vsimko]

• update the introduction paragraph, the package is now called "Road Condition Analysis"
• add "How to cite" section
• add "Who do I talk to?" section
• add "How to contribute" section
• mention somewhere that the generated vignette is available as a HTML page here: https://vsimko.github.io/rroad/

you can use https://github.com/taiyun/corrplot as an inspiration