Restructure to allow usage without built-in locales

[OrKoN]

I am proposing a change to address the issue #204:

The only difference to the plan outlined here #204 (comment) is that I think core.ts would redundant. Instead it's more flexible if every method is separate. I'd use it like this:

import { format } from 'timeago.js/format';
import { register } from 'timeago.js/register'; 

so that realtime.ts and built-in locales can be stripped from my bundle.

What do you think?

[coveralls]

Pull Request Test Coverage Report for Build 481

• 10 of 10 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 53.89%

---

Totals
Change from base Build 479:	0.3%
Covered Lines:	672
Relevant Lines:	1020

---

💛 - Coveralls

[hustcc]

Finally, can you help to show the package size increment?

[OrKoN]

@hustcc how can I see the package size increment? do you mean the size of the resulting bundles? I don't think the size actually changes but it'd be happy to check if you let me know what package size I need to look at and how.

[OrKoN]

Output of npm run build:

> timeago.js@4.0.0 size /home/alex/projects/timeago.js
> size-limit


  gh-pages/timeago.min.js
  Package size: 888 B
  Size limit:   1 KB

  gh-pages/timeago.full.min.js
  Package size: 7.36 KB
  Size limit:   10 KB

  With all dependencies, minified and gzipped

[OrKoN]

Same before the change:

> timeago.js@4.0.0 size /home/alex/projects/timeago.js-original
> size-limit


  gh-pages/timeago.min.js
  Package size: 888 B
  Size limit:   1 KB

  gh-pages/timeago.full.min.js
  Package size: 7.36 KB
  Size limit:   10 KB

  With all dependencies, minified and gzipped

[hustcc]

v4.0.1 released.