Add squabble-disable to prevent squabble from running on a file.

[erik]

Taking a crack at @PhilipTrauner's idea from #6.

This adds support for a new per-file configuration option, which can turn off any syntax/semantic checking for an entire file.

Additionally, this PR updates the per-file configuration keys to use the prefix squabble-.

/* old format (deprecated, but still supported) */
-- enable:ruleA

/* new format */
-- squabble-enable:ruleA

[PhilipTrauner]

Great stuff! Good call on also introducing the squabble- prefix for per-file settings.
What would you think about extending the configuration system even further to allow for line-based ignores?

I've got something like this in mind:

-- squabble-disable-line:RequirePrimaryKey
create table public.foo (
    bar integer not null
);

-- squabble-disable-line
create table public.baz ();

I'd also be more than happy to take a crack at this myself 🙂

[erik]

@PhilipTrauner pglast seems to be a bit inconsistent about location reporting, so my suspicion is that it would be a bit tricky to get per-line configurations working well, but I really like the idea! If you wanted to try it out I would be happy to include that functionality.