Expand episode 1 to include experimental design & batch effects

[jdrnevich]

Episode 1 does not cover what is listed in the questions, particularly "What are the different choices to consider when planning an RNA-seq experiment?". This episode needs to be greatly expanded to include information on experimental design considerations and batch effect avoidance in additional to sequencing and quantification options. See Harvard's excellent https://hbctraining.github.io/Intro-to-rnaseq-hpc-salmon-flipped/lessons/02_experimental_planning_considerations.html and credit them if re-using anything. I also have many slides/graphics that could be added.

[jdrnevich]

The ending Challenge to discuss RNA-Seq quantification went amazing well in-person, but I am afraid it will not go as well on-line.

[csoneson]

Some more content was added in #75 and #76