Gas Type Added in AbiItem

[maektwain]

As suggested by the #3383

Description

Please include a summary of the change and be sure you follow the contributions rules we do provide here

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have selected the correct base branch.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• Any dependent changes have been merged and published in downstream modules.
• I ran npm run dtslint with success and extended the tests and types if necessary.
• I ran npm run test:unit with success.
• I have executed npm run test:cov and my test cases do cover all lines and branches of the added code.
• I ran npm run build-all and tested the resulting file/'s from dist folder in a browser.
• I have updated the CHANGELOG.md file in the root folder.
• I have tested my code on the live network.

[coveralls]

Coverage remained the same at 88.596% when pulling 2e15ff4 on maektwain:1.x into 2a5c5cb on ethereum:1.x.

[cgewecke]

This LGTM - there's a small issue with the changelog that still needs to be resolved - otherwise good to go.

[holgerd77]

Ok, will merge here.