update readme

README.md

@@ -1,3 +1,37 @@
-# Purreads 🐈 🐈‍⬛
+# Purreads 🐈‍⬛
 
-Goodreads clone for cats.
+## What is it?
+
+Purreads is a simple Goodreads clone with a very limited functionality. I initiated it to try out GraphQL with Go.
+
+With Purreads you can create a new ~~user~~ cat, create a new book or add a book to a cats' library as an "in progress" or a "read" book.
+
+Main packages:
+
+- [GORM](https://gorm.io/gorm) for the ORM
+- [PostgreSQL](https://gorm.io/docs/connecting_to_the_database.html#PostgreSQL) as the database
+- [gqlgen](https://github.com/99designs/gqlgen) for the GraphQL server
+
+## Schema
+
+GraphQL schema can be found in [graph/schema.graphqls](graph/schema.graphqls) and resolvers are in [graph/schema.resolvers.go](graph/schema.resolvers.go).
+
+## Usage
+
+Start server by running:
+
+```sh
+$ go run server.go
+```
+
+GraphQL playground will be available at port 8080.
+
+### Updating schema
+
+After updating the GraphQL schema or operations, don't forget to run generate command:
+
+```sh
+$ go generate ./...
+```
+
+This command will update [generated code](graph/generated.go) according to your schema if necessary.