build: add standard-version and commitlint packages

[rafaelss95]

Adds:

• standard-version - a package to generate changelog following specific (in our case Angular) conventions and tags;
• commitlint - a package to validate commit messages (it will really improve the changelog generator). It was configured according to CONTRIBUTING.md;

[loktionov129]

@rafaelss95,
I think this package https://github.com/okonet/lint-staged would be great too for running linters on git staged files.

And it seems to me https://github.com/semantic-release/semantic-release are better than https://github.com/conventional-changelog/standard-version

[rafaelss95]

@loktionov129 Thanks for your suggestions.

We already use lint-staged for running tslint and prettier, however commitlint has another purpose: validate commit messages to generate a good/useful changelog.

While I do like the idea of semantic-release, I don't think it's a good idea to add it here, because not every time we accept a PR, we want to make a release.

[loktionov129]

@rafaelss95 semantic-release makes a release only when adding the commits with feature or fix types, but he doesn't releases the commits with chore/build/ci/docs/perf/refactor/style/test types.

[rafaelss95]

Yep, I know, and also when a PR containing a breaking change is accepted. I believe we don't want this behavior here, @mgechev could you give your thoughts?

[mgechev]

Yes, let's be more explicit.