docs(README): Fix links in README.md

[JamesJHPark]

Which problem is this PR solving?

• Fixes # 2413

Short description of the changes

• This fix is to address the broken links issue in the OpenTelemetry SDK Reference TypeDoc (links to Getting Started, Contributing, Development Guide, Benchmarks, Examples) by replacing the relative URLs with the appropriate absolute URLs in README.md.

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ James (cd9a359, 5120405)

[dyladan]

Love a good doc fix. Sign the CLA and this will merge quickly

[codecov]

Codecov Report

Merging #2463 (4a36e59) into main (a1875b6) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2463      +/-   ##
==========================================
- Coverage   93.22%   93.18%   -0.04%     
==========================================
  Files         137      137              
  Lines        5017     5017              
  Branches     1060     1060              
==========================================
- Hits         4677     4675       -2     
- Misses        340      342       +2     

Impacted Files	Coverage Δ
...emetry-api-metrics/src/platform/node/globalThis.ts	0.00% <0.00%> (-100.00%)	⬇️
...emetry-core/src/platform/node/RandomIdGenerator.ts	87.50% <0.00%> (-6.25%)	⬇️