Graphic design updates

[trevorcampbell]

Polishes many of our hand-made figures to be consistent across the book and look more professional.

• The syntax figures in Ch1, 3
• The table figures in Ch 3
• The CV/testing figures in Ch 6
• The version control workflow figures in Ch 12
• The workflow figure in the preamble
• The file path diagram in Ch 2
• The sampling figure in Ch 10
• (new) Map for the canadian languages example

Also closes a bunch of issues:

• Closes str.split description in wrangling chapter #311
• Closes happiness.csv vs canlang.csv in path example in reading chapter #279
• Closes Incorrect figure text #254
• Closes Mouse hover figure too big in PDF build #250
• Closes Inconsistent axis label code style #224
• Closes Missing syntax fig for assign in Ch1 #191
• Closes Fig 1.5 uses multiline expr before introduction #190
• Closes Minor changes to Ch3 pivot fig/code #94
• Closes Minor change to Ch3 data frame image #93
• Closes Thoughts for plot and image color choices #18
• Closes Figure goes below its own axis #318
• Closes Text in 10.4 needs updating to match the new code #320
• Closes Inference static images from R book #321

Also see the related R PR: UBC-DSCI/introduction-to-datascience#565

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