Update Install doc for bazel build

[lalitb]

Fixes #1032

Changes

• Add doc on including opentelemetry-cpp in existing bazel project
• Fix build-file for curl ( pulled from fix: update curl lib build_file #1041 )

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1046 (0452f89) into main (bf176f3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1046   +/-   ##
=======================================
  Coverage   94.85%   94.85%           
=======================================
  Files         151      151           
  Lines        5971     5971           
=======================================
  Hits         5663     5663           
  Misses        308      308