This patch implements `# runic: on` and `# runic: off` toggle comments
that can be included in the source to toggle formatting on/off.
The two comments i) must be placed on their own lines, ii) must be on
the same level in the expression tree, and iii) must come in pairs. An
exception to condition iii) is made for top level toggle comments so
that formatting for a whole file can be disabled by a `# runic: off`
comment at the top without having to add one also at the end of the
file.
For compatibility with JuliaFormatter, `#! format: (on|off)` is also
supported but it is not possible to pair e.g. a `# runic: off` comment
with a `#! format: on` comment.
Closes#12, closes#41.
Fredrik Ekre
d68512faee