Update README with install instruction, usage, and utility description.

README.org

@@ -2,5 +2,33 @@
 
 #+TITLE: README for Guix-Cantrips
 
-Utilities to make programming with guix feel like magic.
+Utilities to make programming with guix feel like ~magic~.
+
+* Install
+
+Currently, the only way to install is with guix. Add this repo as a channel:
+
+#+BEGIN_SRC scheme
+	(channel
+	 (name 'guix-cantrips)
+	 (url "https://git.solarpunk.moe/TakeV/guix-cantrips.git")
+	 (branch "main")
+	 (introduction
+		(make-channel-introduction
+		 "eae81890ad657de402acd7e2013f4f02376a7bf0"
+		 (openpgp-fingerprint takev-key))))
+#+END_SRC
+
+Then run =guix pull= followed by =guix install guix-cantrips=.
+
+* Usage
+Invoke with =guix-cantrips COMMAND=.
+
+* Utilities
+The current utilities include:
+
+| Utility | Description                                                                                                    |
+|---------+----------------------------------------------------------------------------------------------------------------|
+| summon  | Downloads the source code of the specified package, and extracts it to a project directory (~/src by default). |
+|         | *Please note that this can overwrite the folder in the project directory, should the project already exist.*     |