fix #78: Add additional metadata for function expressions

[ekhaled]

closes #78

[alexprey]

Hi, thanks for changes! Looks very nice.
However, I not sure about data structure changes in SvelteDataItem, I'm think that it is not a good idea to make that type messy. I need a time to think about that and comeback later

[ekhaled]

If you have any suggestions, let me know. Happy to implement it 😄

[alexprey]

Ok, I'm thinking on that and that what I think:
Params and return metadata are used in functions, and actually functions can be used anywhere in the JS code: component can have methods, variables can be a function, parameter can be a function, return type also can be a function. And if you look at JSDocType you can see that I already provide additional information about type. So, let to create a new type for JSDocType:

export interface JSDocTypeFunction extends JSDocTypeBase {
    kind: 'function';
    params?: SvelteMethodParamItem[];
    return?: SvelteMethodReturnItem;
}

and update the following:

export type JSDocType = JSDocTypeElement | JSDocTypeConst | JSDocTypeFunction | JSDocTypeUnion;

I think that is a better way to do that. If you have any ideas or points, please mention that, I'm open for discussion

[ekhaled]

That sounds absolutely fine to me.
Are you able to make the relevant commits and update this PR?

[alexprey]

Ok, I'm update your PR and merge it. Try to do it on this week and plan release for the next week.
Thanks for you contribution!

[alexprey]

@ekhaled thanks for your contribution to that library! Sorry, that I was too much slow to make last fixes and publish the new version of library 🐱