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

@@             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