I will be updating this manual in the coming week or so until it
fully documents every aspect of Ion to end users.

Added `matches` builtin and fixed grammar issue

Handle unusual errors during process spawning

Only print "Command not found: ...", if the error is actually that the command
is not found. Otherwise print a general error description from the system. I
found that while trying to echo to the example scheme (:vec) I was getting
EBADF which caused "command not found: /bin/ion" to be printed.

Some more consistency changes to builtins

Making the builtins a little neater. Closures weren't very friendly for debuggers/backtrace

Case statements are now implicitly ended

Miscellaneous method updates / QoL changes

Add support for inline expressions in methods

Fix issue #419 `echo hello#world`

Updated statement logic for comments so they must be preceded by whitespace or at the start of a line

Read init file only when using interactive shell

Added not builtin

Conditionals && and || weren't working as expected

Jobs no longer use a separate list of builtins to determine the command type

bugfix: echo was treating anything preceded by - as an option flag

Leads to a major speed bonus for script executions, which have
no business creating and managing a context that they'll never
use. IE: the fibonacci script finishes in half the time as
before.