Add README with initial goals and development usage

README.md

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+# AppOS #
+
+<https://github.com/distrust-foundation/appos>
+
+## About ##
+
+A minimal, immutable, and deterministic Linux unikernel build system targeting
+various Trusted Execution Environments for use cases that require high security
+and accountability.
+
+This is intended as a reference repository which could serve as a boilerplate
+to build your own hardened and immutable operating system images for high
+security applications.
+
+## Platforms ##
+
+| Platform                   | Target  | Status   | Verified boot Method |
+|----------------------------|:-------:|:--------:|:--------------------:|
+| Generic/Qemu               | generic | working  | Safeboot or Heads    |
+| AWS Nitro Enclaves         | aws     | building | HOTP via Nitrokey    |
+| GCP Confidential Compute   | gcp     | research | vTPM 2.0 attestation |
+| Azure Confidential VMs     | azure   | research | vTPM 2.0 attestation |
+
+## Features ##
+
+ * Immutability
+   * Root filesystem is a CPIO filesystem extracted to a RamFS at boot
+ * Minimalism
+   * < 5MB footprint
+   * Nothing is included but a kernel and your target binary by default
+   * Sample "hello world" included as a default reference
+   * Debug builds include busybox init shim and drop to a shell
+ * Determinism
+   * Multiple people can build artifacts and get identical hashes
+   * Allows one to prove distributed artifacts correspond to published sources
+ * Hardening
+   * No TCP/IP network support
+     * Favor using a virtual socket or physical interface to a gateway system
+   * Most unessesary kernel features are disabled at compile time
+   * Follow [Kernel Self Protection Project](kspp) recommendations
+
+[  kspp]: https://kernsec.org/wiki/index.php/Kernel_Self_Protection_Project
+
+## Development ##
+
+### Requirements ###
+
+ * 10GB+ free RAM
+ * Docker 20+
+ * GNU Make
+
+### Examples ###
+
+### Build given target
+```
+make TARGET=generic
+```
+
+### Boot generic image in Qemu
+```
+make run
+```
+
+### Enter shell in toolchain environment
+```
+make toolchain-shell
+```
+
+### Update toolchain depedendency pins
+```
+make toolchain-update
+```