User friendly README.md

The existing README does not describe the project or the usage of the tool. I've edited what the author wrote in their software release announcement on GBATemp for the GitHub repository.

README.md

@@ -1,2 +1,57 @@
-# Build
-`mvn package`
+# JNUSTool
+JNUSTool is a Java application for download and decrypting NUS data from the WiiU and 3DS eShop. This tool allows users to browse and select individual files associated with a NUS titlekey before downloading, supports on-the-fly decryption (no cleaning up temporary files!), and allows for high-speed multithreaded downloads.
+
+## Features:
+- Download encrypted data from the eShop
+- Seamlessly decrypt encrypted data from the eShop with on-the-fly decryption
+- Decrypt pre-downloaded NUS data
+- Support for downloading specific versions of a title
+- Download/decrypt of the meta folder only
+- On the fly download and decryption of single files (Updates, DLC, etc.)
+- Bulk title downloads using filelist.txt
+- Bulk downloads using [regular expressions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Cheatsheet) (e.g all models or sounds)
+- Automatically search for and notify of available software updates during download. 
+ 
+## Environment Requirements: 
+- [Java 8](https://www.java.com/en/download/)
+
+## Note: eShop EOL Announcement
+[Nintendo has announced that the WiiU and 3DS eShop will be permanently discontinued on or before March 2023.](https://en-americas-support.nintendo.com/app/answers/detail/a_id/57847) This tool will lose full download functionality at that time. 
+
+# Usage
+There are two ways to run this application.
+1. Automated:
+Run the JNUSTool.jar file. Make sure you have a `config` file (with correct values) and `updatetitles.csv` in the same directory. A windows will popup and let you choose from the game updates. Feel free to add more titles.
+
+2. Command line (when you want to provide a key or use a titleid that is not in the list)
+
+`java -jar JNUSTool.jar <TITLEID>`
+
+To download a specific version, specify the version after the title ID.
+
+e.g. `java -jar JNUSTool.jar <titlekey> v16`
+
+To disable on-the-fly decryption, append the string `-dlEncrypted`
+
+Specific files, or a batch of specific files can be downloaded in isolation by appending `-file <file path or regex>` to the command 
+
+e.g. 
+- Download only app.xml with: `java -jar JNUSTool.jar <titlekey>  -file /code/app.xml`
+- Download only code folder with: `java -jar JNUSTool.jar <titlekey>  -file /code/.*`
+- Download all .szs files with: `java -jar JNUSTool.jar <titlekey>  -file .*.szs`
+
+## Sample config file
+```
+http://maschell.de/ccs/download
+EE10040260BBB4ABD2C42DB25570B656
+updatetitles.csv
+TAGAYA 1 (latest_version)
+TAGAYA 2 (versionlist)
+```
+
+# Data sources
+The software will not work without the required titlekey, commonkey, and Nintendo URL - which can not be included here for legal purposes. GBATemp, Reddit, and other internet sources would be a good place to look. :stuck_out_tongue_winking_eye:
+
+# Additional Information
+- [GBATemp: JNUSTool Release Announcement](https://gbatemp.net/threads/jnustool-nusgrabber-and-cdecrypt-combined.413179/)
+- [hacks.guide homebrew guides](https://hacks.guide/)