Typedef fixes

[kookster]

I saw some other PRs for typedefs that weren't right and the typedefs for cart chunk and related other chunks were pretty vague, so this fixes those issues, and the export style - this obviously builds off PR #14 :

Bug:

• toSampleRate(samples: number, ...) — parameter should be sampleRate, not samples

Chunk types are all object — these should have proper interfaces:

• fact — has chunkId, chunkSize, dwSampleLength
• cue — has chunkId, chunkSize, dwCuePoints, points (array of point objects)
• smpl — has 12 fields plus loops array (each with 6 fields)
• bext — has 17 fields (BWF metadata)
• mext — has 7 fields (MPEG extension)
• cart — has 22 fields including postTimer array
• iXML, _PMX — have chunkId, chunkSize, value
• ds64 — has 9 fields (RF64 size info)
• junk — has chunkId, chunkSize, chunkData

Missing from fmt type:

• MPEG fields (headLayer, headBitRate, headMode, headModeExt, headEmphasis, headFlags, ptsLow, ptsHigh) — should be optional

Return types too vague:

• listTags() returns object — should be Record<string, string>
• listCuePoints() returns Array — should have a CuePoint interface with all 15 fields

  Missing method:

  • getLISTIndex(listType: string): number | null — public method on WaveFileTagEditor

  Export style:

  • Uses export = wavefile / declare namespace (CJS-style). Now that the package has "type": "module" and ESM exports, this should use export class WaveFile instead.