* doc/README.md:
- Fix a couple of typos.
- Fix spacing and shell quote style (for consistency with other markdown docs
already in the tree).
- Fix indent with spaces not tabs in heredocs with <<- style¹.
- Fix shell example partially inserted twice.
* doc/*.pow:
- Fix indent with spaces not tabs in heredocs with <<- style¹.
¹: See the last paragraph in
https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Here-Documents
"If the redirection operator is ‘<<-’, then all leading tab characters
are stripped from input lines and the line containing delimiter. This allows
here-documents within shell scripts to be indented in a natural fashion."
