Add polygon network to Ethereum Connector

[Lohann]

Description

Add polygon config to ethereum connector

Type of change

• New feature (non-breaking change which adds functionality)

Code review prechecks:

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Inline comments have been added for each method
• I have made corresponding changes to the documentation
• Code changes introduces no new problems or warnings
• Test cases have been added
• Dependent changes have been merged and published in downstream modules

[4meta5]

should add Polygon to Blockchain enum like in this PR right #175

[Lohann]

@4meta5 done!

[4meta5]

I still do not see any changes to the enum Blockchain. We need to add Blockchain::Polygon right?

[Lohann]

@4meta5 Blockchain::Polygon only exists on master branch, which we merge the connector into the timechain, the staging environment is still using the connector as a service, which don't have the enum Blockchain