feat: add scripts to add/remove/get relayer from icon bridge contracts

[izyak]

Closes #ISSUE-NUMBER

Checklist:

• [x] I have performed a self-review of my own code
• [ ] I have documented my code in accordance with the documentation guidelines
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have run the unit tests
• [x] I only have one commit (if not, squash them into one commit).
• [x] I have a descriptive commit message that adheres to the commit message guidelines

Please review the CONTRIBUTING.md file for detailed contributing guidelines.

[codecov[bot]]

Codecov Report

Merging #871 (147e417) into main (43e7ce3) will increase coverage by 0.04%. Report is 1 commits behind head on main. The diff coverage is n/a.

Additional details and impacted files

[](https://app.codecov.io/gh/icon-project/icon-bridge/pull/871?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=icon-project) ```diff @@ Coverage Diff @@ ## main #871 +/- ## ============================================ + Coverage 36.39% 36.43% +0.04% Complexity 811 811 ============================================ Files 125 125 Lines 12061 12061 Branches 1091 1091 ============================================ + Hits 4389 4394 +5 + Misses 7332 7327 -5 Partials 340 340 ``` [see 1 file with indirect coverage changes](https://app.codecov.io/gh/icon-project/icon-bridge/pull/871/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=icon-project)