feat: split "long code blocks" rule into suggestion and warning

[dwilding]

Resolves #149

Includes a fix from #174 to set MinAlertLevel = suggestion in vale.ini.

[SecondSkoll]

Two things here (applies to the 25 line one as well).

1. In MyST MD it's best practice to separate options from content:

::: {code} text
:foo: bar

Content

Your implementation doesn't quite cover this case - blank lines after the :option: are captured and count for the total number of lines.

2. I think you thought of this but it's likely a copy error - but the ``` based rule doesn't ignore ` characters in the repeated section so it can spill over the initial block.

[dwilding]

Thanks @SecondSkoll, these turned out to be non-trivial to fix.

1. I've changed the relevant parts of the rules to:

((:[^\n]+:[^\n]*\n)+\n){0,1}

which requires the options block (if any) to end with a blank line. I tried to also allow no blank line after the options block, but that caused the blank line in the test case to be captured as part of the code - the behaviour we want to avoid.

Maybe there's some way to get this spot on, but it seems fiddly. Since having a blank line is best practice, I think it's good enough to only cover that case. If we really care, we could have a separate rule that flags no-blank-line-after-options. Topic for another day.

2. Ideally, we shouldn't ignore ` in the repeated section. We also shouldn't ignore :, which is the current behaviour. Ignoring : was actually masking that the ``` based rule could spill over: My test case contained this line after a short codeblock:

But 26 lines is NOT acceptable:

Which contains :, and so was sneakily preventing the rule from spilling over 🤯

What we ideally want is for each line in the repeated section to either:

• be blank, or
• not start with ``` and not start with : (to prevent the rule from greedily gobbling the options at this point instead of earlier)

Here's what I ended up with:

(\n|(?!```)[^:\n][^\n]*\n){26,}```

And similarly for the : based rule. Edit: I suppose ((?!```)(?!:)[^\n]*\n){26,}``` would work too, and is arguably simpler.

[SecondSkoll]

Looks great, just pushed the changes we reviewed together.