Translation of LB4 docs to portuguese

[newtonsbm]

• Initial configuration for a new language (pt-br / LB4)
• Translated index.md

[bschrammIBM]

Thank you for the translation, I have forwarded it to the technical team.

[bschrammIBM]

Please add the following statement in English on the index.md page "This is a community translation into Portuguese. For the latest information, see the English version." "English version" should be a hyperlink to http://loopback.io/doc/en/lb4/index.html

[dhmlau]

@newtonsbm , thanks for translating the documentation for LB4! Please keep in mind that LB4 is in Developer Preview #1, therefore there might be lots of changes in a near future. Stay tuned!

Could you please rebase your PR and fix the commit messages? It shows the 2 messages below exceed the 50 characters limit. Thanks.

Linting commit logs
**
**  2 problems found:
**    b98cfa7 - adds a warning about the community translation to p: First line should be 50 characters or less (saw 55)
**    be821a8 - Merge branch 'gh-pages' of github.com:strongloop/lo: First line should be 50 characters or less (saw 74)
**

[bschrammIBM]

You will need to rebase so this can be merged.

[newtonsbm]

Ok, I've never done rebase before, I'm following this guide here but it still did not work out. I think it's because I've merge at first. I will keep trying.

[dhmlau]

Looks like it worked! Your PR has landed. Thanks for your contribution!