Update docs (#3)

CONTRIBUTING.md

@@ -0,0 +1,8 @@
+# Contributing
+
+Contributions are welcome. Submit a pull request or open an issue as necessary.
+
+## Developer Prerequisites
+
+* [Docker](https://docs.docker.com/get-docker/)
+* [.NET 5.0 SDK](https://docs.microsoft.com/dotnet/core/install/)

README.md

@@ -1,2 +1,71 @@
-# dredge
-Dredge: A Docker Registry Client CLI
+# Dredge: A Docker Registry Client CLI
+
+Dredge is a CLI built on .NET that provides a simple way to execute commands on a Docker registry's HTTP API. Currently, only read operations are supported.
+
+## Install
+
+Dredge is published as a [.NET tool](https://docs.microsoft.com/en-us/dotnet/core/tools/global-tools) and available as a [NuGet package](https://www.nuget.org/packages/Valleysoft.Dredge).
+
+### Installing as a global tool
+
+```console
+> dotnet tool install -g Valleysoft.Dredge
+```
+
+## Usage
+
+### Notes
+
+> * Dredge relies on your credentials already being stored in your environment when targeting registries that require authentication. For those registries you need to run `docker login` (for Docker Hub) or `docker login <registry>` before running Dredge.
+> * Dredge targets the Docker Hub registry by default but can be configured to target other registries by using the `-r` or `--registry` option.
+
+### Query Repositories
+
+```console
+> dredge repo list -r contoso.azurecr.io
+[
+  "myrepo/app"
+  "myrepo/app2"
+]
+```
+
+### Query Tags
+
+```console
+> dredge tag list myrepo/app -r contoso.azurecr.io
+[
+  "1.0",
+  "1.1"
+]
+```
+
+### Query Manifest
+
+```console
+> dredge manifest get myrepo/app 1.0 -r contoso.azurecr.io
+{
+  "config": {
+    "mediaType": "application/vnd.docker.container.image.v1+json",
+    "size": 1508,
+    "digest": "sha256:a5f12aa2470df1d32034c6707c8041158b652f38d2a9ae3d7ad7e7532d22ebe0",
+    "urls": []
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
+      "size": 2796860,
+      "digest": "sha256:927c0c94c7c576fff0792aca7ec73d67a2f7f4cb3a6e53a84559337260b36964",
+      "urls": []
+    }
+  ],
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "schemaVersion": 2
+}
+```
+
+### Query Digest
+
+```console
+> dredge manifest digest myrepo/app 1.0 -r contoso.azurecr.io
+sha256:95202993700f8cd7aba8496c2d0e57be0666e80b4c441925fc6f9361fa81d10e
+```