(split)Typed CSSOM values support (cssinjs#887)

* added fallbacks test to fn rules

* only call onChangeValue if plugins: true

* enable removing props from fn rules

* shorter syntax with coercion

* wip full syntax support

* restore browsers.json

* changelog

* move hook call to the core

* isProcessed flag explanation

* added tests to fn rules

* remove media rule as a function test case

* added a test for cssinjs#796, as part of cssinjs#682

* tests for compose plugin

* observables

- move documentation to the package
- update docs, since plugins don't apply by default
- introduce option process: true to the plugin to enable plugins if user wants that

* move fn values docs

* wording

* support typed cssom

* Update docs/json-api.md

* Update changelog.md

.size-snapshot.json

@@ -1,13 +1,13 @@
 {
   "dist/react-jss.js": {
-    "bundled": 125452,
-    "minified": 43742,
-    "gzipped": 13078
+    "bundled": 125073,
+    "minified": 43593,
+    "gzipped": 13026
   },
   "dist/react-jss.min.js": {
-    "bundled": 102044,
-    "minified": 36571,
-    "gzipped": 10983
+    "bundled": 101665,
+    "minified": 36422,
+    "gzipped": 10932
   },
   "dist/react-jss.cjs.js": {
     "bundled": 16755,