Add BUILD.md

Author: ljwagerfield

BUILD.md

@@ -0,0 +1,41 @@
+# Building From Source
+
+This repository contains a hot-reloading sandbox for developing the `@upload-io/react-uploader` NPM package.
+
+## Prerequisites
+
+`node` and `npm` are required — we actively support the following versions:
+
+| Package | Version  |
+| ------- | -------- |
+| Node    | v18.12.1 |
+| NPM     | v8.19.2  |
+
+## How To Build & Run
+
+### 1. Clone
+
+```shell
+git clone git@github.com:upload-io/react-uploader.git
+cd react-uploader
+```
+
+### 2. Setup Environment
+
+```
+export NODE_OPTIONS=--openssl-legacy-provider
+```
+
+### 3. Install Dependencies
+
+```shell
+npm install
+```
+
+### 4. Run The Tests
+
+```shell
+npm test
+```
+
+Note: there is no hot-reloading demo for `react-uploader`. Please see the `uploader` repository instead.