Providing a complete list of item skins for the user to select from

[SVijayB]

Description

Changes made to the application in this update :

• Added an Update.py file to update local data for the list of skins.
• Update.py also shows last updated date and time.
• Extracted Item skin names are then searched through to pick desired item's skins.
• All the item skins are then listed for the user to pick, instead of the user having to enter the data manually.
• Removed knives since Steam's API support is not provided for them.

Related Issue

This PR closes #8

Motivation and Context

Since the API is case sensitive and the spaces provided have to be precise, that is, the names of the items have to match Steam's CSGO database. It was redundant to ask the user to enter the item name without having to Google it. And that makes the application useless.

This update fixes that problem by providing a complete list of item skins for the user to pick from.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.

[SVijayB]

Have to update the documentation as well before merging the pull request.