fix(svelte): parse Content-Type properly when directives are also specified in getResponseBody

[jchen42703]

Fixes #20 and bumps version to 0.0.6 to make upgrading easier

[lietu]

Thanks for the PR and suggestion.

I would rather split from ; and take the left part for comparison, it's optional, but anything to the right of it can be ignored for these purposes. Also checking if the individual strings are contained in it does not mean it "starts with" it, and even if it starts with it - there might be something else relevant after that, so it may in some rare cases have issues.

Could you update the PR so that is extracted before doing the JSON_CONTENT_TYPES.includes -check with the result?

[jchen42703]

@lietu I decided to call the .split in the .includes call since if contentType &&.. enforces a non-null string, which makes some of the typing clearer. It's a little ugly, but I think it's relatively clear?