Sort the output of the built-in 'export' and 'alias' commands, in cases
where all environment variables/aliases are printed out.

This patches fixes a bug, where sometimes, when a Rune::String was
detected, the resulting string from the string!() macro wasn't getting
pushed to the current verse.

Previously, the recite() function created the 'out' variable, which was
a String, that got passed to the various incant functions, in order to
capture STDOUT in certain situations. In cases where STDOUT was
captured, it was first converted to a String, and then appended to the
'out' variable, by means of String::from_utf8_lossy(). This works for
basic text, however, does NOT work for binary data. This becomes
problematic, when for example, downling a tar file with curl/wget, that
is then piped ('|') to the tar program. Using from_utf8_lossy() in this
case can corrupt the tar file. This patch makes it so that out is stored
as bytes by default, and only converted to a String when necessary.

Instead of handling aliases in the recite() function, which requires two
loops to handle properly with the current implementation, offload
checking for aliases to the read() function.

Make sure to interpret alias values as their own poems, since aliases
can be fairly complex.

Add documentation for anthology::lookup(), with a list containing all
the default aliases for builtin commands.

Add docstring comments for all the incant function throughout the
anthology, documenting what each function does, and an example of it's
shell command.

Previously, if an environment variable was given in a string, such as:
'$PATH' or "$PATH", both would be replaced with the value of $PATH from
the environment. However, for single quotes strings, any values inside
should be taken at face value. In other words, echo '$PATH' should
simply write out: $PATH, and not whatever environment value $PATH
happens to be. This patch replaced '$' in single quoted strings with
the ASCII shift out (x0e) character. Any ASCII SO placeholder is
replaced with a '$' in recite(), after the environment variables have
been accounted for.

Instead of passing a hard-coded value for the prompt, use $PS1. The
default is '|> ', set in dist/etc/dwvshrc.

Replaced all (non-test) instances of env!("HOME") with env::var("HOME").
The env! macro should only be used in instances where the environment
variable should be resolved during compile time.