feat: loose parsing mode

[dummdidumm]

Related to #4818

Adds a loose parsing mode which will continue parsing no matter what. In loose mode, the first error that is encountered is part of the return in case subsequent analysis of the result cannot be performed and a fallback to the original error is needed.
This would enable sveltejs/language-tools#1177
It's up to discussion whether the naming is good and whether or not additional parsing fallbacks should be applied in loose mode (this is the simplest implementation as a start for now).

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Tests

• Run the tests with npm test and lint the project with npm run lint

[Rich-Harris]

this was superseded by #14691, closing