Fix findItemsByKeywords and eslint fixes

• Fix find items by keyword method.
• some eslint fixes.

Added docsify support for better documentation

• Fix CI build failure.
• Integerate docsify with ebay node api.

Added FindItemsAdvanced api support

• Integerated with ebay advanced api support.

Added findItemsByProduct support and extended findItemsByKeyword method

2.7.2

version bump

Support for Custom headers, code clean up using utils

Support for adding custom headers (#54)

* create common utils across project

* add support for custom headers

* override eslint config

Added findCompletedItems across eBay

• Integerated with findCompletedItems api

Minor enhancement

• #42
• #42

Bug Fix: Space in search Keyword

Fixed #39

Integerated Shopping Api

• Included ebay shopping Api.
• Bug fixes.

Feature: Get Most Watched items and Most Similar items

Get Most Watched items and Most Similar items