chore(gatsby): Migrate reducers/index to TypeScript (#23877)

* Change file extension from JS to TS

* Change reducer config export to ES6 module

* Change imports and exports to ES6 modules

* Change reducers import on redux index to use ES6 modules

* Update reducers imports and exports

* Comment unused codes

* Update merge conflicts

* Update nodesReducer module name

* Update last-action state type

* Fix merge conflicts

* Revert api test snapshot

* ops, actually fix merge conflicts

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

yarn.lock

@@ -2251,7 +2251,12 @@
   dependencies:
     "@types/node" "*"
 
-"@types/node@*", "@types/node@^8.5.7":
+"@types/node@*":
+  version "14.0.6"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-14.0.6.tgz#f9e178b2da31a4b0ec60b64649e244c31ce18daf"
+  integrity sha512-FbNmu4F67d3oZMWBV6Y4MaPER+0EpE9eIYf2yaHhCWovc1dlXCZkqGX4NLHfVVr6umt20TNBdRzrNJIzIKfdbw==
+
+"@types/node@^8.5.7":
   version "8.10.61"
   resolved "https://registry.yarnpkg.com/@types/node/-/node-8.10.61.tgz#d299136ce54bcaf1abaa4a487f9e4bedf6b0d393"
   integrity sha512-l+zSbvT8TPRaCxL1l9cwHCb0tSqGAGcjPJFItGGYat5oCTiq1uQQKYg5m7AF1mgnEBzFXGLJ2LRmNjtreRX76Q==