For the validate function, index.d.ts declares:
Here is the relevant code from index.js:
WasmModule.prototype.validate = function (options) {
var features = new Features(options || ({}));
index.d.ts is missing a description of the options parameter. Ferreting around in the code, it looks like elsewhere in index.d.ts, WasmFeatures is defined, which seems to be intended to match the WebAssembly feature list described here.
I think that index.d.ts should say:
validate(options?: WasmFeatures): void;