chore: react-sdk | downgrading react peer dependency | react 18.0.0 -…

…> 16.8.0 (#742)

## This PR fix the npm warning when installing @openfeature/react-sdk in
application using react version < 18

| Package   | Change   | Passing   | Confidence   |
|-----------|----------|-----------|--------------|
| [react](https://github.com/facebook/react) |
[18.0.0](https://github.com/facebook/react/releases/tag/v18.0.0) ->
[16.8.0](https://github.com/facebook/react/releases/tag/v16.8.0) | True
| High |

Fixes #741

### How to test
1. create a react project using react 16.8.0, node 14, npm 6.X.X
2. install @openfeature/react-sdk
3. Observe no install warning
4. use `useFeatureFlag` in application as per documentation with no
issue.

Signed-off-by: Shujaat Ali <dr.shujaat_ali@hotmail.com>
Co-authored-by: Todd Baert <todd.baert@dynatrace.com>

packages/react/package.json

@@ -47,7 +47,7 @@
   "homepage": "https://github.com/open-feature/js-sdk#readme",
   "peerDependencies": {
     "@openfeature/web-sdk": ">=0.4.0",
-    "react": ">=18.0.0"
+    "react": ">=16.8.0"
   },
   "devDependencies": {
     "@openfeature/core": "*",