Update shim versions

With a few additions to the psc-package.json file I was able to get a
page using purescript-react working. I saved the gist here:
https://gist.github.com/hdgarrood/828a40781d155fe74d91f1332ceaa922

Author: hdgarrood

client/src/Try/Shim.purs

@@ -12,15 +12,15 @@ type Shim =
 shims :: Object Shim
 shims = Object.fromFoldable
   [ Tuple "react"
-      { url: "https://unpkg.com/react@16.6.3/umd/react.development.js"
+      { url: "https://unpkg.com/react@16.13.0/umd/react.development.js"
       , deps: []
       }
   , Tuple "react-dom"
-      { url: "https://unpkg.com/react-dom@16.6.3/umd/react-dom.development.js"
+      { url: "https://unpkg.com/react-dom@16.13.0/umd/react-dom.development.js"
       , deps: [ "react" ]
       }
   , Tuple "react-dom/server"
-      { url: "https://unpkg.com/react-dom@16.6.3/umd/react-dom-server.browser.development.js"
+      { url: "https://unpkg.com/react-dom@16.13.0/umd/react-dom-server.browser.development.js"
       , deps: [ "react" ]
       }
   ]

staging/core/psc-package.json

@@ -34,6 +34,8 @@
         "proxy",
         "quickcheck",
         "random",
+        "react",
+        "react-dom",
         "record",
         "refs",
         "semirings",
@@ -44,6 +46,8 @@
         "tuples",
         "typelevel-prelude",
         "unfoldable",
-        "validation"
+        "validation",
+        "web-dom",
+        "web-html"
     ]
 }