docs: move react-native docs to separate section (#387)

* link to React Native readme section from rng error
* For linkability, move react-native docs to separate section.
* Link to readme in src/rng-browser.js

Co-Authored-By: Robert Kieffer <robert@broofa.com>

README.md

@@ -12,6 +12,7 @@ For the creation of [RFC4122](http://www.ietf.org/rfc/rfc4122.txt) UUIDs
   - Node 8, 10, 12
   - Chrome, Safari, Firefox, Edge, IE 11 browsers
   - Webpack and rollup.js module bundlers
+  - React Native ([see note](#getrandomvalues-not-supported))
 - **Secure** - Cryptographically-strong random values
 - **Small** - Zero-dependency, small footprint, plays nice with "tree shaking" packagers
 - **CLI** - Includes the [`uuid` command line](#command-line) utility
@@ -35,8 +36,6 @@ versions, all of which are supported here. In order of popularity, they are:
 
 **Unsure which one to use?** Use version 4 (random) unless you have a specific need for one of the other versions. See also [this FAQ](https://github.com/tc39/proposal-uuid#faq).
 
-**Are you using React Native?** If you are using this library from React Native, you need to add a polyfill for `crypto.getRandomValues`. We recommend using [`react-native-get-random-values`](https://github.com/LinusU/react-native-get-random-values#readme).
-
 ### Create Version 4 (Random) UUIDs
 
 ```javascript
@@ -336,6 +335,16 @@ Available bundles:
 - https://unpkg.com/uuid@latest/dist/umd/
 - https://cdn.jsdelivr.net/npm/uuid@latest/dist/umd/
 
+## "getRandomValues() not supported"
+
+This error occurs in environments where the standard
+[`crypto.getRandomValues()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues)
+API is not supported. This issue can be resolved by adding an appropriate polyfill:
+
+| Environment  | Suggested Polyfill                                                                                  |
+| ------------ | --------------------------------------------------------------------------------------------------- |
+| React Native | [`react-native-get-random-values`](https://github.com/LinusU/react-native-get-random-values#readme) |
+
 ## Upgrading From uuid\@3
 
 "_Wait... what happened to uuid\@4 - uuid\@6?!?_"

README_js.md

@@ -25,6 +25,7 @@ For the creation of [RFC4122](http://www.ietf.org/rfc/rfc4122.txt) UUIDs
   - Node 8, 10, 12
   - Chrome, Safari, Firefox, Edge, IE 11 browsers
   - Webpack and rollup.js module bundlers
+  - React Native ([see note](#getrandomvalues-not-supported))
 - **Secure** - Cryptographically-strong random values
 - **Small** - Zero-dependency, small footprint, plays nice with "tree shaking" packagers
 - **CLI** - Includes the [`uuid` command line](#command-line) utility
@@ -48,8 +49,6 @@ versions, all of which are supported here. In order of popularity, they are:
 
 **Unsure which one to use?** Use version 4 (random) unless you have a specific need for one of the other versions. See also [this FAQ](https://github.com/tc39/proposal-uuid#faq).
 
-**Are you using React Native?** If you are using this library from React Native, you need to add a polyfill for `crypto.getRandomValues`. We recommend using [`react-native-get-random-values`](https://github.com/LinusU/react-native-get-random-values#readme).
-
 ### Create Version 4 (Random) UUIDs
 
 ```javascript --run v4
@@ -325,6 +324,16 @@ Available bundles:
 - https://unpkg.com/uuid@latest/dist/umd/
 - https://cdn.jsdelivr.net/npm/uuid@latest/dist/umd/
 
+## "getRandomValues() not supported"
+
+This error occurs in environments where the standard
+[`crypto.getRandomValues()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues)
+API is not supported. This issue can be resolved by adding an appropriate polyfill:
+
+| Environment  | Suggested Polyfill                                                                                  |
+| ------------ | --------------------------------------------------------------------------------------------------- |
+| React Native | [`react-native-get-random-values`](https://github.com/LinusU/react-native-get-random-values#readme) |
+
 ## Upgrading From uuid\@3
 
 "_Wait... what happened to uuid\@4 - uuid\@6?!?_"

src/rng-browser.js

@@ -14,7 +14,7 @@ var rnds8 = new Uint8Array(16); // eslint-disable-line no-undef
 export default function rng() {
   if (!getRandomValues) {
     throw new Error(
-      'uuid: This browser does not seem to support crypto.getRandomValues(). If you need to support this browser, please provide a custom random number generator through options.rng.',
+      'crypto.getRandomValues() not supported. See https://github.com/uuidjs/uuid#getrandomvalues-not-supported',
     );
   }
   return getRandomValues(rnds8);