don't signal an error on BioC when knit2html() an Rmd vignette that appears to be an Rmd v2 document (i.e. has YAML metadata)

export wrap() and is_low_change() to allow rgl (and other) graphics systems to work like base graphics (#1892)

fix #1595 by automatically adding {} before [

revert the fix for #1595 b91452e to fix haozhu233/kableExtra#607

skip the check for dependency on markdown/rmarkdown on BioC (#1864)

reminder package authors of installing rmarkdown to be able to build R Markdown vignettes: https://github.com/yihui/knitr/issues/1864#issuecomment-821489943