Improved FormData support; (#4448)

[jasonsaayman]

• Fixed isFormData predicate;
  Added support for automatic object serialization to FormData if Content-Type is multipart/form-data;
  Added support for FormData to be overloaded using config.env.FormData option;
  Added support for FormData in node.js environment through form-data package;

• Added the form-data package as a dependency for the server build;
  Added tests for FormData payload;

• Added FormData automatic serialization section;
  Refactored cancellation section;

• Reworked toFormData helper;
  Expose toFormData helper as a static method;
  Refactored transform request;
  Added kindOf, kindOfTest, endsWith, isTypedArray util;
  Refactored utils.js to use kindOf for tests;

• Fixed isFormData predicate; (Fixed isFormData predicate; #4413)

Added support for automatic object serialization to FormData if Content-Type is multipart/form-data;
Added support for FormData to be overloaded using config.env.FormData option;
Added support for FormData in node.js environment using form-data package;

(cherry picked from commit 73e3bdb)

• Added shortcut methods postForm, putForm, patchForm to submit a Form;
  Added ability to submit FileList object as a FormData;
  Updated README.md;

• Updated README.md;

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