refactor: pubsub (#467)

* feat: peer-store v0

* chore: apply suggestions from code review

Co-Authored-By: Jacob Heun <jacobheun@gmail.com>

* chore: address review

* refactor: pubsub subsystem

* chore: address review

* chore: use topology interface

* chore: address review

* chore: address review

* chore: simplify tests

test/pubsub/utils.js

@@ -0,0 +1,29 @@
+'use strict'
+
+const Gossipsub = require('libp2p-gossipsub')
+const { multicodec } = require('libp2p-gossipsub')
+const Crypto = require('../../src/insecure/plaintext')
+const Muxer = require('libp2p-mplex')
+const Transport = require('libp2p-tcp')
+
+const mergeOptions = require('merge-options')
+
+const baseOptions = {
+  modules: {
+    transport: [Transport],
+    streamMuxer: [Muxer],
+    connEncryption: [Crypto]
+  }
+}
+
+module.exports.baseOptions = baseOptions
+
+const subsystemOptions = mergeOptions(baseOptions, {
+  modules: {
+    pubsub: Gossipsub
+  }
+})
+
+module.exports.subsystemOptions = subsystemOptions
+
+module.exports.subsystemMulticodecs = [multicodec]