fix(SingleThreadedFragmentsModel)!: expose raw arg defaulting to false

[ShaMan123]

Description

SingleThreadedFragmentsModel#save and SingleThreadedFragmentsModel#edit returned a raw buffer. This does not align with the rest of the API, which defaults to false.
I have exposed raw as a last arg defaulting to false.
Should we add a comment that runtime editing should use raw in order to avoid deflating/inflating for performance reasons?

fixes #186 (comment)

Additional context

Before this fix

const model = new SingleThreadedFragmentsModel("my-model", buffer);
const newBuf = model.save();
new SingleThreadedFragmentsModel("my-model", newBuf); // fails
new SingleThreadedFragmentsModel("my-model", newBuf, true); // succeeds

After this fix

const model = new SingleThreadedFragmentsModel("my-model", buffer);
const newBuf = model.save();
new SingleThreadedFragmentsModel("my-model", newBuf);
const newRawBuf = model.save(true);
new SingleThreadedFragmentsModel("my-model", newBuf, true);

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following:

• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
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• Ideally, include relevant tests that fail without this PR but pass with it.

[ShaMan123]

done

[ShaMan123]

updated description