Enhance README consistency across OpenTelemetry components

[Copilot]

This PR addresses inconsistencies in README files across OpenTelemetry Rust components to provide a uniform documentation experience for users.

Changes Made

Enhanced opentelemetry-http README

• Added comprehensive "What does this crate contain?" section detailing:
  • Context propagation capabilities
  • HTTP client support (reqwest, hyper)
  • Exporter utilities
  • Sampling strategy support
• Added "Related crates" section linking to core OpenTelemetry components
• Improved description clarity with explicit OpenTelemetry integration mention

Improved opentelemetry-stdout README

• Enhanced description to clearly explain educational/debugging purpose
• Improved "What does this crate contain?" section with detailed descriptions of:
  • Trace exporter functionality
  • Metrics exporter capabilities
  • Logs exporter features
• Clarified human-readable output format and use cases

Fixed opentelemetry-proto README

• Added missing badges (crates.io, docs.rs, LICENSE, CI, Slack)
• Improved description clarity and formatting
• Added "Getting started" section for consistency

Enhanced opentelemetry-appender-log README

• Added missing "Getting started" section
• Added complete "Supported Rust Versions" section
• Added missing reference links

Updated opentelemetry-semantic-conventions README

• Added missing "Getting started" section for consistency

Structure Consistency

All README files now follow a consistent structure:

1. Title with OpenTelemetry logo
2. Clear description with purpose
3. Complete badge set (crates.io, docs.rs, LICENSE, CI, Slack)
4. Overview section
5. "What does this crate contain?" section (where applicable)
6. "Getting started" section linking to docs
7. Release notes section
8. Supported Rust versions section

This ensures users can easily navigate documentation and find relevant information across all OpenTelemetry Rust components.

Fixes #1306.

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[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: cijothomas / name: Cijo Thomas (d9ea1e6)
• ✅ Unknown (e5acfc5, 7da8d44, 6f990f5)

[cijothomas]

@copilot
make sure the following is checked for every crate in this repo (except examples)

All README files now follow a consistent structure:

Title with OpenTelemetry logo
Clear description with purpose
Complete badge set (crates.io, docs.rs, LICENSE, CI, Slack)
Overview section
"What does this crate contain?" section (where applicable)
"Getting started" section linking to docs
Release notes section
Supported Rust versions section

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.1%. Comparing base (0462369) to head (d9ea1e6).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3074   +/-   ##
=====================================
  Coverage   80.1%   80.1%           
=====================================
  Files        126     126           
  Lines      21957   21957           
=====================================
  Hits       17603   17603           
  Misses      4354    4354           

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[Copilot]

@copilot
make sure the following is checked for every crate in this repo (except examples)

...

Completed comprehensive README consistency check for all OpenTelemetry Rust crates. All 12 crates now follow the required structure:

✅ Title with OpenTelemetry logo
✅ Clear description with purpose
✅ Complete badge set (crates.io, docs.rs, LICENSE, CI, Slack)
✅ Overview section
✅ "What does this crate contain?" section (where applicable)
✅ "Getting started" section linking to docs
✅ Release notes section
✅ Supported Rust versions section

Changes in commit 6f990f5.

[cijothomas]

/easycla

[lukaszgryglicki]

/easycla

[lukaszgryglicki]

@cijothomas EasyCLA now passes as requested on slack.