Migrate to TypeScript

[saihaj]

• Enable strict mode
• compare .d.ts and remove them
• Use tsc to generate .d.ts
• use npm@7 to install stuff

[codecov]

Codecov Report

Merging #340 (661214a) into main (06633c3) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 661214a differs from pull request most recent head 266ecf0. Consider uploading reports for the commit 266ecf0 to get more accurate results

@@            Coverage Diff            @@
##              main      #340   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines          746       746           
  Branches        51        51           
=========================================
  Hits           746       746           

Impacted Files	Coverage Δ
src/__testUtils__/__tests__/dedent-test.ts	100.00% <ø> (ø)
src/__testUtils__/dedent.ts	100.00% <ø> (ø)
src/__tests__/starWarsConnection-test.ts	100.00% <ø> (ø)
src/__tests__/starWarsMutation-test.ts	100.00% <ø> (ø)
src/__tests__/starWarsObjectIdentification-test.ts	100.00% <ø> (ø)
src/__tests__/starWarsSchema.ts	100.00% <ø> (ø)
src/connection/__tests__/arrayConnection-test.ts	100.00% <ø> (ø)
src/connection/__tests__/connection-test.ts	100.00% <ø> (ø)
src/connection/arrayConnection.ts	100.00% <ø> (ø)
src/connection/connection.ts	100.00% <ø> (ø)
... and 11 more

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