README

Update version number manually in title.tex.

To create the PDF version of the manual, go to 'src' and run 'make NimbleUserManual.pdf'.

To create the HTML version of the manual, go to 'src' and run 'make NimbleUserManual.html'.

2022-01-13: I changed the #cha:foo refs to #cha-foo as as of recent bookdown, the ':' is no longer changed to '-' in generating the .html file names, so the rendering would produce file names such as cha:welcome-nimble.html.