Add Code Examples

[dnavarrom]

Type of issue

• [ ] Bug

• [X] Idea/Suggestion

• [ ] Question

Description (include any screenshots or debugging information if applicable)

Provide examples to implement filters and options from AWS Cost Explorer Documentation to save developer time providing specific usage scenarios (which is the primary purpose of this library). Steps:

• Pick any use case and use this example to write your sample https://github.com/dnavarrom/aws-cost-explorer/blob/master/examples/getCostByService.js
• Add the file to https://github.com/dnavarrom/aws-cost-explorer/blob/master/examples/ folder
• Then submit your Pull request. If you need any help, then comment below!