extracted url for scripts into variable

[danish9039]

Which problem is this PR solving?

• part of [jaeger-idl] Reproduce linting checks from the main repo jaeger#6570

Description of the changes

• extracted https://raw.githubusercontent.com/jaegertracing/jaeger/main/scripts into a variable $(SCRIPTS_URL) Reproduce linting checks from the main repo #121 (comment)

How was this change tested?

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• I have added unit tests for the new functionality
• I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: npm run lint and npm run test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.85%. Comparing base (86b800d) to head (94170c9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #141   +/-   ##
=======================================
  Coverage   87.85%   87.85%           
=======================================
  Files          12       12           
  Lines         568      568           
=======================================
  Hits          499      499           
  Misses         67       67           
  Partials        2        2           

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