(fix) npmignore improve

[eromano]

Please check if the PR fulfills these requirements

[x] The commit message follows our [guidelines](https://github.com/Alfresco/alfresco-js-api/wiki/Commit-format)
[x] Tests for the changes have been added (for bug fixes / features)
[x] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] Documentation
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)
src and other file should not be in the bundle

What is the new behavior?

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[ ] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[eromano]

#1083

[garth]

Is this change in the latest 4.4.0-beta30? I still have src folder with ts files in node_modules.

(the latest beta's don't seem to be tagged in the repo, so it's not easy to see what's included in each release)