Add description requirement to meta requirement

[adthrasher]

wdl/wdl-lint/src/rules/missing_metas.rs

Line 57 in cf378af

fn missing_section(name: &str, section: Section, context: Context, span: Span) -> Diagnostic {

This rule should notify users that the newly added meta section must include a description key or the user will immediately receive a new lint warning from DescriptionMissing.

[a-frantz]

This problem sparked an idea for "linking" rules. I imagine the output of sprocket explain MissingMetas saying You should also look at 'DescriptionMissing' (or something to that effect). This linkage would go in one direction. Presumably a user invoking sprocket explain DescriptionMissing has already written meta sections and shouldn't be linked back to MissingMetas.

The Rule trait could have a new method fn linked_rules() -> Vec<&'static str> where the Vec contains other Rule IDs.

The above text is a tangent and has been migrated to its own issue (#173). This issue should remain focused on clarifying explanation() text

[a-frantz]

We probably have other explanation() text that could use wordsmithing. Whoever gets around to rewording the MissingMetas rule, I'd encourage them to take a pass at our other lint rules too!