Fix docs and translate into portuguese

[luizcmarin]

In https://github.com/yiisoft/form/pull/317 new docs writing. Wait it.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (35af441) to head (7eaab8e). Report is 31 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #324   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
+ Complexity       774       770    -4     
===========================================
  Files             48        47    -1     
  Lines           2511      2501   -10     
===========================================
- Hits            2511      2501   -10     

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[vjik]

In #317 new docs writing. Wait it.