Add links to linter warning details on use.ink

[Michael Müller]

The warnings that our linter outputs look like this:

Each lint is documented in more detail at e.g. https://use.ink/linter/rules/strict_balance_equality.

Atm of writing this we haven't switched the default content of use.ink to 5.x, but that'll happen today and then the link will work. Right now it's https://use.ink/5.x/linter/rules/strict_balance_equality.

Please put a link to the details for each linting rule on use.ink into the warning message.