Assess the exercises

[njtierney]

See how the exercises in

https://github.com/njtierney/rmd4sci/tree/master/exercises

Link up to the outline described here:

https://njtierney.github.io/rmd4sci/index.html

cc @PatrickRobotham

[PatrickRobotham]

01-rmd-example:
Should be linked in Chapter 4 "Getting Started"

02-rmd-figures-chunks:
Should be linked in Chapter 5 "Figures and Tables".

03-rmd-lm-tables-inline-eqn:
Unclear where to link this. Chapter 5 again maybe?

04-rmd-global-opts-device:
Should be linked to Chapter 6 "HTML, PDF, and Word (and more!)"

05-rmd-bib-polish:
Should be linked to Chapter 7: Citations

06-rmd-find-errors:
Should be linked to Chapter 10: Common Problems