Update contribution guidelines per latest development changes (#10792)

* Update contribution guidelines per latest
- Fix package.json node engine version to have more explicit error messages
- Add .nvmrc for easier integration with nvm

* Remove extraneous steps

* Use previous version
Locking at CVE-2020-1971 https://nodejs.org/en/blog/release/v14.15.4/

* Use >= to prevent unique version id

.nvmrc

@@ -0,0 +1 @@
+14.15.4

CONTRIBUTING.md

@@ -9,9 +9,9 @@ Install the Xcode Command Line Tools Package
 xcode-select --install
 ```
 
-Install [node.js](https://nodejs.org/) version ^10.15 ( Minimum 10.15 while sticking only to major version 10.0 )
+Install [node.js](https://nodejs.org/) version 14
 ```bash
-brew install node
+brew install node@14
 ```
 Install [yarn](https://yarnpkg.com/en/)
 ```bash
@@ -25,15 +25,15 @@ git clone [email protected]:mapbox/mapbox-gl-js.git
 
 Install node module dependencies
 ```bash
-cd mapbox-gl-js &&
 yarn install
 ```
 
 ### Linux
 
-Install [git](https://git-scm.com/), [node.js](https://nodejs.org/) (version ^10.15), [GNU Make](http://www.gnu.org/software/make/), and libglew-dev
+Install [git](https://git-scm.com/), [node.js](https://nodejs.org/) version 14, [GNU Make](http://www.gnu.org/software/make/), and libglew-dev
 ```bash
-sudo apt-get update &&
+sudo apt-get update
+curl -sL https://deb.nodesource.com/setup_14.x | sudo bash -
 sudo apt-get install build-essential git nodejs libglew-dev libxi-dev
 ```
 
@@ -50,13 +50,12 @@ git clone [email protected]:mapbox/mapbox-gl-js.git
 
 Install node module dependencies
 ```bash
-cd mapbox-gl-js &&
 yarn install
 ```
 
 ### Windows
 
-Install [git](https://git-scm.com/), [node.js](https://nodejs.org/) (version ^10.15), [yarn](https://yarnpkg.com/en/docs/install#windows-tab), [npm and node-gyp](https://github.com/Microsoft/nodejs-guidelines/blob/master/windows-environment.md#compiling-native-addon-modules).
+Install [git](https://git-scm.com/), [node.js](https://nodejs.org/) version 14, [yarn](https://yarnpkg.com/en/docs/install#windows-tab), [npm and node-gyp](https://github.com/Microsoft/nodejs-guidelines/blob/master/windows-environment.md#compiling-native-addon-modules).
 
 Clone the repository
 ```bash
@@ -66,7 +65,6 @@ git clone [email protected]:mapbox/mapbox-gl-js.git
 
 Install node module dependencies
 ```bash
-cd mapbox-gl-js
 yarn install
 ```
 

package.json

@@ -11,7 +11,7 @@
     "url": "git://github.com/mapbox/mapbox-gl-js.git"
   },
   "engines": {
-    "node": ">=6.4.0"
+    "node": ">=14.15.4"
   },
   "dependencies": {
     "@mapbox/geojson-rewind": "^0.5.0",