Add description for docker-compose-elasticsearch.yml

[pipiland2612]

Which problem is this PR solving?

• Part of [W1]: SPM Development environment #7142

Description of the changes

• Add description for docker-compose-elasticsearch.yml in docker-compose/monitor/README.md

How was this change tested?

• make lint test

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 96.21%. Comparing base (eb85aa5) to head (e48069d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7146      +/-   ##
==========================================
- Coverage   96.22%   96.21%   -0.02%     
==========================================
  Files         358      358              
  Lines       21689    21689              
==========================================
- Hits        20870    20867       -3     
- Misses        613      615       +2     
- Partials      206      207       +1     

Flag	Coverage Δ
badger_v1	9.90% <ø> (ø)
badger_v2	2.05% <ø> (ø)
cassandra-4.x-v1-manual	14.89% <ø> (ø)
cassandra-4.x-v2-auto	2.04% <ø> (ø)
cassandra-4.x-v2-manual	2.04% <ø> (ø)
cassandra-5.x-v1-manual	14.89% <ø> (ø)
cassandra-5.x-v2-auto	2.04% <ø> (ø)
cassandra-5.x-v2-manual	2.04% <ø> (ø)
elasticsearch-6.x-v1	20.23% <ø> (ø)
elasticsearch-7.x-v1	20.31% <ø> (ø)
elasticsearch-8.x-v1	20.49% <ø> (ø)
elasticsearch-8.x-v2	2.05% <ø> (ø)
grpc_v1	11.44% <ø> (ø)
grpc_v2	2.05% <ø> (ø)
kafka-3.x-v1	10.17% <ø> (ø)
kafka-3.x-v2	2.05% <ø> (ø)
memory_v2	2.05% <ø> (ø)
opensearch-1.x-v1	20.36% <ø> (ø)
opensearch-2.x-v1	20.36% <ø> (ø)
opensearch-2.x-v2	2.05% <ø> (ø)
query	2.05% <ø> (ø)
tailsampling-processor	0.55% <ø> (ø)
unittests	95.03% <ø> (-0.02%)	⬇️

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