added an api changelog for this release

Author: hzoppetti

src/content/changelog/4-78-3-2020-10-20-2020.md

@@ -0,0 +1,12 @@
+---
+title: '4.78.3: 2020-10-20'
+date: 2020-10-20T04:00:00.000Z
+version: 4.78.3
+changelog:
+  - API
+---
+
+### Changed
+- The [API v4 spec](http://www.linode.com/docs/api) has been moved to reside in the new [Linode Docs site](http://www.linode.com/docs). The links within the spec file have been updated to reflect this new location.
+
+- All links within [API changelog](https://developers.linode.com/changelog/api/) entries have been updated to reflect the new location of the [API v4 spec](http://www.linode.com/docs/api) file.