Add explanatory images and text for “The rules for missing values in Boolean algebra”

[yingjie02]

I am a beginner in R and feel that this part is a bit difficult to understand, so I am trying to supplement this part of the content

The rules for missing values in Boolean algebra seem to be attempting to connect circuits

"&" is the extension of another section of the line on the basis of the line, and it is only "True" when the entire line is connected

"|" is to add a line next to the line. If either the original line or the supplementary line is connected, it is "True"

I assign the copyright of this contribution to Hadley Wickham