chore: update deps and add generated types

[achingbrain]

Updates bl to pull in new buffer and also generates types from source
as the hand-written ones were incomplete.

[codecov]

Codecov Report

Merging #13 (7fef365) into master (3e1e040) will decrease coverage by 0.69%.
The diff coverage is 96.29%.

❗ Current head 7fef365 differs from pull request most recent head d1f39e9. Consider uploading reports for the commit d1f39e9 to get more accurate results

@@            Coverage Diff             @@
##           master      #13      +/-   ##
==========================================
- Coverage   98.38%   97.69%   -0.70%     
==========================================
  Files           7        7              
  Lines         124      130       +6     
==========================================
+ Hits          122      127       +5     
- Misses          2        3       +1     

Impacted Files	Coverage Δ
src/index.js	100.00% <ø> (ø)
src/int32BE-decode.js	100.00% <ø> (ø)
src/int32BE-encode.js	100.00% <ø> (ø)
src/varint-encode.js	100.00% <ø> (ø)
src/decode.js	95.65% <95.45%> (-1.23%)	⬇️
src/encode.js	100.00% <100.00%> (ø)
src/varint-decode.js	100.00% <100.00%> (ø)

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[alanshaw]

LGTM