rename `config.DefaultHeaders` to `config.RequestHeaders`

bump version

Merge pull request #71 from chargebee/release-v3.47.0

Release v3.47.0

Merge pull request #70 from chargebee/release-v3.46.1

Releasing v3.46.1.

Merge pull request #69 from chargebee/release-v3.46.0

Release v3.46.0

install goimports-reviser if not exist

Merge pull request #68 from chargebee/release-v3.45.0

Release v3.45.0

update readme to v4

Merge pull request #64 from chargebee/release/sdk-go/v3.44.0

Releasing v3.44.0

Merge pull request #62 from chargebee/release/sdk-go/v3.43.0

Releasing v3.43.0