[couchbase] missing implementation for MutableDocument setValue

[KG3RK3N]

I found a issue with the setValue method on the MutableDocument.
In the packages/nativescript-couchbase/index.d.ts there is the method defined, but the implementation is missing on iOS and android.

It should have the following implementations:

packages/nativescript-couchbase/index.android.ts

	setValue(key: string, value: ValueType): this {
		const native = valueToObject(value);
		if (native !== undefined) {
			this.native.setValue(key, native);
		}
		return this;
	}

packages/nativescript-couchbase/index.ios.ts

	setValue(key: string, value: ValueType): this {
		const native = valueToObject(value);
		if (native !== undefined) {
			this.native.setValueForKey(native, key);
		}
		return this;
	}