Headings should be surrounded by blank lines
Rationale: Aside from aesthetic reasons, some parsers, including kramdown, will not parse headings that don't have a blank line before, and will parse them as regular text.
Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>
* Update "Ways to set environment variables in Compose"
Add information about setting variables explicitly to get a warning from Compose if variables are not set
* Fix link to interpolation docs