Drop ESM support (#2366)

* Drop ESM support

* Add `"unpkg"` field

stream/package.json

@@ -3,7 +3,6 @@
   "version": "2.0.0",
   "description": "Streaming data, mithril-style",
   "main": "stream.js",
-  "module": "stream.mjs",
   "directories": {
     "test": "tests"
   },

stream/stream.mjs

@@ -1,172 +0,0 @@
-/* eslint-enable */
-Stream.SKIP = {}
-Stream.lift = lift
-Stream.scan = scan
-Stream.merge = merge
-Stream.combine = combine
-Stream.scanMerge = scanMerge
-Stream["fantasy-land/of"] = Stream
-
-var warnedHalt = false
-Object.defineProperty(Stream, "HALT", {
-	get: function() {
-		warnedHalt || console.log("HALT is deprecated and has been renamed to SKIP");
-		warnedHalt = true
-		return Stream.SKIP
-	}
-})
-
-function Stream(value) {
-	var dependentStreams = []
-	var dependentFns = []
-
-	function stream(v) {
-		if (arguments.length && v !== Stream.SKIP) {
-			value = v
-			if (open(stream)) {
-				stream.changing()
-				stream.state = "active"
-				dependentStreams.forEach(function(s, i) { s(dependentFns[i](value)) })
-			}
-		}
-
-		return value
-	}
-
-	stream.constructor = Stream
-	stream.state = arguments.length && value !== Stream.SKIP ? "active" : "pending"
-	stream.parents = []
-
-	stream.changing = function() {
-		open(stream) && (stream.state = "changing")
-		dependentStreams.forEach(function(s) {
-			s.changing()
-		})
-	}
-
-	stream.map = function(fn, ignoreInitial) {
-		var target = stream.state === "active" && ignoreInitial !== Stream.SKIP
-			? Stream(fn(value))
-			: Stream()
-		target.parents.push(stream)
-
-		dependentStreams.push(target)
-		dependentFns.push(fn)
-		return target
-	}
-
-	var end
-	function createEnd() {
-		end = Stream()
-		end.map(function(value) {
-			if (value === true) {
-				stream.parents.forEach(function (p) {p.unregisterChild(stream)})
-				stream.state = "ended"
-				stream.parents.length = dependentStreams.length = dependentFns.length = 0
-			}
-			return value
-		})
-		return end
-	}
-
-	stream.toJSON = function() { return value != null && typeof value.toJSON === "function" ? value.toJSON() : value }
-
-	stream["fantasy-land/map"] = stream.map
-	stream["fantasy-land/ap"] = function(x) { return combine(function(s1, s2) { return s1()(s2()) }, [x, stream]) }
-
-	stream.unregisterChild = function(child) {
-		var childIndex = dependentStreams.indexOf(child)
-		if (childIndex !== -1) {
-			dependentStreams.splice(childIndex, 1)
-			dependentFns.splice(childIndex, 1)
-		}
-	}
-
-	Object.defineProperty(stream, "end", {
-		get: function() { return end || createEnd() }
-	})
-
-	return stream
-}
-
-function combine(fn, streams) {
-	var ready = streams.every(function(s) {
-		if (s.constructor !== Stream)
-			throw new Error("Ensure that each item passed to stream.combine/stream.merge/lift is a stream")
-		return s.state === "active"
-	})
-	var stream = ready
-		? Stream(fn.apply(null, streams.concat([streams])))
-		: Stream()
-
-	var changed = []
-
-	var mappers = streams.map(function(s) {
-		return s.map(function(value) {
-			changed.push(s)
-			if (ready || streams.every(function(s) { return s.state !== "pending" })) {
-				ready = true
-				stream(fn.apply(null, streams.concat([changed])))
-				changed = []
-			}
-			return value
-		}, Stream.SKIP)
-	})
-
-	var endStream = stream.end.map(function(value) {
-		if (value === true) {
-			mappers.forEach(function(mapper) { mapper.end(true) })
-			endStream.end(true)
-		}
-		return undefined
-	})
-
-	return stream
-}
-
-function merge(streams) {
-	return combine(function() { return streams.map(function(s) { return s() }) }, streams)
-}
-
-function scan(fn, acc, origin) {
-	var stream = origin.map(function(v) {
-		var next = fn(acc, v)
-		if (next !== Stream.SKIP) acc = next
-		return next
-	})
-	stream(acc)
-	return stream
-}
-
-function scanMerge(tuples, seed) {
-	var streams = tuples.map(function(tuple) { return tuple[0] })
-
-	var stream = combine(function() {
-		var changed = arguments[arguments.length - 1]
-		streams.forEach(function(stream, i) {
-			if (changed.indexOf(stream) > -1)
-				seed = tuples[i][1](seed, stream())
-		})
-
-		return seed
-	}, streams)
-
-	stream(seed)
-
-	return stream
-}
-
-function lift() {
-	var fn = arguments[0]
-	var streams = Array.prototype.slice.call(arguments, 1)
-	return merge(streams).map(function(streams) {
-		return fn.apply(undefined, streams)
-	})
-}
-
-function open(s) {
-	return s.state === "pending" || s.state === "active" || s.state === "changing"
-}
-
-
-export default Stream