chore: release proposal 0.21.0

[dyladan]

This will be released using npm dist tag @next. This will prevent users who run npm install @opentelemetry/api from getting this version unless they specifically ask for it by running npm install @opentelemetry/api@next or npm install @opentelemetry/api@0.21.0.

When core and contrib 0.21.0 versions have also been released with @next tag, all packages will get the @latest tag at the same time. This will prevent users from accidentally installing incompatible versions.

For the future I recommend we do all releases in this fashion.

💥 Breaking Change

• #78 feat: unify signatures of with and bind (@Rauno56)
• #46 chore: do not export singletons (@dyladan)

🚀 Enhancement

• #81 chore: function overloads implementation of startActiveSpan in noop t… (@naseemkullah)

🏠 Internal

• #84 chore: remove unused backwards compatibility folder (@Flarna)
• #85 chore: add node:16 to the test matrix (@Rauno56)
• #63 feat: debug log global registrations and logger overwrites (@Rauno56)
• #75 Add CodeQL Security Scan (@xukaren)
• #79 chore: fix eslint config (@Rauno56)

Committers: 5

• Daniel Dyla (@dyladan)
• Gerhard Stöbich (@Flarna)
• Karen Xu (@xukaren)
• Naseem (@naseemkullah)
• Rauno Viskus (@Rauno56)

[codecov]

Codecov Report

Merging #88 (3f4cc45) into main (d28c68e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #88   +/-   ##
=======================================
  Coverage   94.83%   94.83%           
=======================================
  Files          42       42           
  Lines         561      561           
  Branches       87       87           
=======================================
  Hits          532      532           
  Misses         29       29           

Impacted Files	Coverage Δ
src/version.ts	100.00% <100.00%> (ø)

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