Add engines 16 to @jbrowse/img

[cmdcolin]

This is required, unless we want to add a AbortController poly/ponyfill

On node 12 and node 14 it produces this error

 jb2export --bigwig src/jbrowse-components/test_data/volvox/volvox-sorted.bam.coverage.bw --loc ctgA:1000-2000 --fasta src/jbrowse-components/test_data/volvox/volvox.fa
(node:1965899) UnhandledPromiseRejectionWarning: ReferenceError: AbortController is not defined
    at _callee$ (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@jbrowse/core/util/index.js:881:15)
    at tryCatch (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/regenerator-runtime/runtime.js:63:40)
    at Generator.invoke [as _invoke] (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/regenerator-runtime/runtime.js:294:22)
    at Generator.next (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/regenerator-runtime/runtime.js:119:21)
    at asyncGeneratorStep (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@babel/runtime/helpers/asyncToGenerator.js:3:24)
    at _next (/home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@babel/runtime/helpers/asyncToGenerator.js:25:9)
    at /home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@babel/runtime/helpers/asyncToGenerator.js:32:7
    at new Promise (<anonymous>)
    at /home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@babel/runtime/helpers/asyncToGenerator.js:21:12
    at /home/cdiesh/.nvm/versions/node/v12.22.7/lib/node_modules/@jbrowse/img/node_modules/@jbrowse/core/util/index.js:918:19
(node:1965899) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:1965899) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

[codecov]

Codecov Report

Merging #2727 (d35c667) into main (b43ed81) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2727      +/-   ##
==========================================
- Coverage   60.75%   60.73%   -0.02%     
==========================================
  Files         561      561              
  Lines       26346    26346              
  Branches     6424     6424              
==========================================
- Hits        16007    16002       -5     
- Misses      10013    10018       +5     
  Partials      326      326              

Impacted Files	Coverage Δ
...nts/src/SNPCoverageRenderer/SNPCoverageRenderer.ts	66.05% <0.00%> (-5.51%)	⬇️
...ckages/core/pluggableElementTypes/RpcMethodType.ts	85.41% <0.00%> (+2.08%)	⬆️

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