Integrate with PackXZExtract to support pack.xz libs.

All pack.xz libraries now have their MD5s properly calculated.
Sha1 validations are performed on jar libraries. The checksums
forge provides for compressed files are neither the sha1 or md5
of the initial or extracted file. Ignoring those for now.

Still TODO is integration with baseurl. Might move both that
and base path to the .env file to reduce redundency in command processing.

README.md

@@ -2,6 +2,23 @@
 
 Generate a distribution.json for Helios.
 
+## Requirements
+
+* Node.js 12
+* Java 8+ (https://adoptopenjdk.net/)
+  * This is required to process [XZ](https://tukaani.org/xz/format.html) files.
+
+## Setup
+
+1. Clone the repository
+2. Install the dependencies (`npm i`)
+3. Create a `.env` file at the root directory and set the required values.
+
+Example
+```properties
+JAVA_EXECUTABLE=C:\Program Files\AdoptOpenJDK\jdk-8.0.222.10-hotspot\bin\java.exe
+```
+
 ## Usage
 
 Nebula is not complete. The following usage is tentative.