Single migrate page.

Fixes #641

Author: cristianoc

data/sidebar_react_latest.json

@@ -2,7 +2,7 @@
   "Overview": [
     "introduction",
     "installation",
-    "migrate-from-v3"
+    "migrate-react"
   ],
   "Main Concepts": [
     "elements-and-jsx",

data/sidebar_react_v0100.json

@@ -2,7 +2,7 @@
   "Overview": [
     "introduction",
     "installation",
-    "migrate-from-reason-react"
+    "migrate-react"
   ],
   "Main Concepts": [
     "elements-and-jsx",

pages/docs/react/latest/installation.mdx

@@ -28,7 +28,7 @@ Then add the following setting to your existing `bsconfig.json`:
 
 > The [new jsx transform](https://ko.reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) of ReactJS is available with `mode: "automatic"`.
 
-**Note** JSX v4 is newly introduced with the idomatic record-based representation of component. If your dependecies are not compatible with v4 yet, then you can use v3 in the same project. Check out the details in [Migrate from v3](/docs/react/latest/migrate-from-v3)
+**Note** JSX v4 is newly introduced with the idomatic record-based representation of component. If your dependecies are not compatible with v4 yet, then you can use v3 in the same project. Check out the details in [Migrate from v3](/docs/react/latest/migrate-react)
 
 To test your setup, create a new `.res` file in your source directory and add the following code:
 

pages/docs/react/latest/migrate-from-v3.mdx renamed to pages/docs/react/latest/migrate-react.mdx

@@ -1,7 +1,7 @@
 ---
 title: Migrate from JSX v3
 description: "Migrate from JSX v3"
-canonical: "/docs/react/latest/migrate-from-v3"
+canonical: "/docs/react/latest/migrate-react"
 ---
 
 # Migrate from JSX v3

pages/docs/react/v0.10.0/migrate-from-reason-react.mdx renamed to pages/docs/react/v0.10.0/migrate-react.mdx

@@ -1,7 +1,7 @@
 ---
 title: Migrate from ReasonReact
 description: "Migrate from ReasonReact"
-canonical: "/docs/react/latest/migrate-from-reason-react"
+canonical: "/docs/react/latest/migrate-react"
 ---
 
 # Migrate from ReasonReact