Splits contribution into separate file for better organisation

[NejcZdovc]

Resolves brave/brave-browser#1987

Native implementation: brave-intl/bat-native-ledger#168

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

• make sure that contribution is still working

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[NejcZdovc]

@kjozwiak @rebron @srirambv can we please uplift this to 57? This is part of refactors changes that will be needed to implement retries that are targeted for 57 as well.

[tmancey]

👍

[NejcZdovc]

master (0.59) c6f623d
0.58.x b503544
0.57.x 3477975

[kjozwiak]

@NejcZdovc approved uplift to 0.57.x BETA after deliberating with @srirambv & @rebron! 👍