Make bms and bmson package TypeScripted

[dtinth]

This PR:

• Creates a new base tsconfig, tsconfig.lib.json for TS-based libraries. Sub-projects should migrate to this base config (only libraries, not CLI tools, so e.g. bemuse-tools are exempt).

  • JS files no longer allowed. This is required for us to be able to generate .d.ts files for consumers (until Allow --declaration with --allowJs microsoft/TypeScript#7546 is resolved)

• Migrates packages/bms to TypeScript.

• Migrates packages/bmson to TypeScript.

[codecov-io]

Codecov Report

Merging #520 into master will decrease coverage by 1.21%.
The diff coverage is 85%.

@@            Coverage Diff             @@
##           master     #520      +/-   ##
==========================================
- Coverage   83.25%   82.04%   -1.22%     
==========================================
  Files         172      167       -5     
  Lines        5423     5129     -294     
  Branches        1       68      +67     
==========================================
- Hits         4515     4208     -307     
+ Misses        908      903       -5     
- Partials        0       18      +18

Impacted Files	Coverage Δ
packages/bms/src/notes/channels.ts	100% <ø> (ø)
packages/bms/src/util/lodash.ts	100% <ø> (ø)
packages/bms/src/bms/chart.ts	100% <100%> (ø)
packages/bms/src/notes/note.ts	100% <100%> (ø)
packages/bms/src/util/match.ts	100% <100%> (ø)
packages/bms/src/bms/objects.ts	84.21% <100%> (ø)
...ges/bms/src/reader/getReaderOptionsFromFilename.ts	37.5% <100%> (ø)
packages/bms/src/bms/headers.ts	80% <100%> (ø)
packages/bms/src/time-signatures/index.ts	92.3% <100%> (ø)
packages/bms/src/notes/index.ts	94.11% <100%> (ø)
... and 17 more

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