[JS] Implement changes to ensure flatbuffer alignment

[asfimport]

See description in parent bug on requirements.

@TheNeuralBit  or [~paul.e.taylor] do you think one of you would be able to pick this up for 0.15.0

Reporter: Micah Kornfield / @emkornfield
Assignee: Paul Taylor / @trxcllnt

PRs and other links:

• GitHub Pull Request #5225

_{Note: This issue was originally created as ARROW-6317. Please see the migration documentation for further details.}

[asfimport]

Brian Hulette / @TheNeuralBit:
I can take a look tonight.

[asfimport]

Wes McKinney / @wesm:
[~paul.e.taylor] wrote on the mailing list that he would also take a look, so maybe double check so work isn't duplicated =)

[asfimport]

Brian Hulette / @TheNeuralBit:
oh! so he did, thanks for letting me know. I'll assign this to [~paul.e.taylor] for now then. I'm happy to pick this up if you don't have time though.

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 5225
#5225