Update UPGRADE.md

Author: andrewosh

UPGRADE.md

@@ -1,12 +1,12 @@
 If you're migrating from `corestore-swarm-networking` v5 to `@corestore/networker` v1, there have been a few breaking changes to be aware of:
 
-### `join`/`leave` -> `configure`
+#### `join`/`leave` -> `configure`
 `join` and `leave` have been replaced by a single method, `configure`, which takes the options `announce`, `lookup`, and `flushed`. 
 
 Using `configure`, a `join` is `configure(discoveryKey, { announce: true, lookup: true }` and a `leave` is `configure(discoveryKey, { announce: false, lookup: false })`
 
-### The `status` method
+#### The `status` method
 The `status` method previously just fowarded Hyperswarm's `status`. It now returns the current network configuration for a given discovery key. To get the Hyperswarm status directly, you can do `networker.swarm.status`.
 
-### Other Assorted Changes
+#### Other Assorted Changes
 * The public `streams` and `peers` properties are now `Set`s instead of Arrays.