docs(README): Give the project a proper README

* Intro
* Background of the update process of Nextcloud
* Usage: Troubleshooting and tips section
* Development: Making changes, using the Makefile, building properly

Signed-off-by: Josh <josh.t.richards@gmail.com>

README.md

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+# 🤖 Updater ⬆️
+
+This app makes it possible to update an existing Nextcloud Server installation in an automated or 
+semi-automated fashion. When you initiate an update of your Nextcloud Server (either from the command-line 
+via `updater.phar` or via the Web UI) this is the app that is triggered.
+
+> [!TIP]
+> If your installation is broken, your environment does not meet our system requirements, or you are doing
+> something exotic, the automated Updater may not be appropriate. Your use case and circumstances may require
+> you to follow the manual update process described in the Maintenance chapter of the [Nextcloud Admin Manual](https://docs.nextcloud.com).
+
+## Background
+
+Fully updating an existing Nextcloud environment, at a high-level, consists of:
+
+- Determing which update paths exists for the in-place Nextcloud Server installation then alerting the admin of their
+availability and explaining their requirements and trade-offs
+- Confirming and preparing the in-use installation (e.g. detecting any currently enabled apps that are incompatible with the target
+Nextcloud version, triggering some repair and pre-update preparation environment changes)
+- Updating the Nextcloud Server software safely (e.g. handling client connections appropriately during the update, verifying the
+integrity of the software package, checking the requirements of the runtime environment, handling unexpected problems that arise
+during any of the update steps, replacing the existing installation files with new ones, utilizing any customizations you made to your
+config that are meant to influence the update process, and keeping your data protected)
+- Running the database migrations (i.e. adjusting your installation's existing database tables to accomodate changes
+required by the new version of Nextcloud Server).
+- Updating existing apps
+
+The Updater app focuses on item #1. After the Updater finishes successfully, item #2 is handled either by manually 
+running `occ upgrade` from the command-line or allowing the Updater app to trigger it for you. Once the database 
+migrations finish, your Nextcloud Server is running the targeted version of the software.
+
+> [!IMPORTANT]
+> A complete upgrade of an existing installation also requires running database migrations which this app does handle directly (though
+> it does offer to run `occ upgrade` on your behalf when the Server application code has been successfully updated.
+
+## How it works
+
+The Updater
+
+## Useful commands and tips
+
+* `updater.log`
+* `updater.phar`
+* occ repair command that resets step files/folders safely/cleanly
+
+## Additional Information
+
+### Development History
+
+* Issue #1: https://github.com/nextcloud/updater/issues/1
+* Issue #2: https://github.com/nextcloud/updater/issues/2
+
+### Design Goals
+
+- Simple
+- Independent of Server itself
+- Robust enough handle server timeouts and connectivity losses
+- Cleanly handles clients that attempt to connect to Server while an update is in progress
+- Verifies the integrity of installation package before deploying
+- Sanity checks the environment before attempting an update (e.g. permissions, etc.)
+- Usable from both the command-line and the web
+- The web facing piece capable appearing "integrated" into the admin's existing Nextcloud Server Web UI experience
+- Reliable across different different types of filesystems
+- Built-in real-time reporting as well as debug logging to ease different types of troubleshooting scenarios
+- Distributable with the standard Server installation package
+- Optionally capable of rolling back updating the installation if any step fails (note: does not cover database migrations failures)
+- Optionally capable of triggering the database migrations required to finish a full Server upgrade