Migrate server code to TypeScript

[nellh]

Completing our migration to typescript for the server package.

[codecov]

Codecov Report

Merging #2931 (359570e) into master (2c46b00) will increase coverage by 0.05%.
The diff coverage is 76.47%.

@@            Coverage Diff             @@
##           master    #2931      +/-   ##
==========================================
+ Coverage   86.93%   86.98%   +0.05%     
==========================================
  Files         383      379       -4     
  Lines       65030    64914     -116     
  Branches     1170     1171       +1     
==========================================
- Hits        56534    56468      -66     
+ Misses       8490     8444      -46     
+ Partials        6        2       -4     

Files	Coverage Δ
packages/openneuro-server/src/__mocks__/config.ts	100.00% <ø> (ø)
packages/openneuro-server/src/config.ts	100.00% <ø> (ø)
packages/openneuro-server/src/datalad/analytics.ts	25.00% <ø> (ø)
packages/openneuro-server/src/datalad/changelog.ts	83.33% <100.00%> (ø)
packages/openneuro-server/src/datalad/dataset.ts	41.73% <100.00%> (ø)
...ckages/openneuro-server/src/datalad/description.ts	74.32% <100.00%> (ø)
...ackages/openneuro-server/src/datalad/pagination.ts	93.40% <ø> (ø)
packages/openneuro-server/src/datalad/readme.ts	28.20% <ø> (ø)
...enneuro-server/src/elasticsearch/elastic-client.ts	100.00% <100.00%> (ø)
...nneuro-server/src/elasticsearch/reindex-dataset.ts	77.50% <100.00%> (ø)
... and 26 more

... and 1 file with indirect coverage changes

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