replace_block: Conditionally replace code in a block of lines
In AlexsLemonade/exrcise: Selectively Excise Code Chunks for Exercises

Conditionally replace code in a block of lines

1	replace_block(block, replace_flags, replacement, comment)

`block`	A character vector of lines from an Rmarkdown document that are either a section of text or a code chunk.
`replace_flags`	A character vector of code chunk options that if set to TRUE will have their code replaced.
`replacement`	A character vector that code chunks will be replaced with, one element per line.
`comment`	TRUE or FALSE; whether to include comments.