Change max-width large pixel amounts to 70ch where relevant

[kylemh]

There are many elements that have large pixel amounts as values for a max-width property to make the content seem bordered, consistent, and collected. In many of those places, a value of 70ch is better than XXXpx. For example, in globalStyles.css the max-width of the p tag is responsively set to different values with media queries. Instead, it should simply always be set to max-width: 70ch. There are other locations where max-width is used in the same way that can be changed.