xfun 0.49

• Added an argument use_block = FALSE to protect_math(). When use_block = TRUE, a $$ $$ expression that spans across multiple lines will be protected in a code block.

• protect_math() will ignore $ $ if there are backticks after the opening $ or before the closing $, e.g., $`this is not math`$.

• protect_math() allows for parentheses () around math expressions now, e.g., ($x$) was previously not recognized but is recognized now (thanks, @AlbertLei, yihui/litedown#34).

• record() works with quote() now (thanks, @ben-schwen, yihui/litedown#38).

• html_escape() will not escape double quotes (i.e., convert "" to ") by default, and the conversion will be done only for html_escape(attr = TRUE).

• The arguments before and after of read_all() can take functions of two arguments now, with the second argument being the content of each file.

• Added an argument start to make_fence().