docs(README): update README for the new format, add better examples

[skip ci]

README.md

@@ -1,10 +1,50 @@
 # Nixlets
 
 This repository contains utilities for creating Nixlets and a collection of Nixlets. \
-Nixlets are kinda like Helm Charts but they are defined using Kubenix and the Nix language. \
+Nixlets are kinda like Helm Charts, but they are defined using Kubenix and the Nix language. \
 \
-One can import the Flake and use the renderNixlet function to turn values (like in Helm) into Kubernetes manifests in YAML.
+One can load Nixlets either via Nix Flakes or by fetching a tarball
 
-## Examples
+
+## Usage
+
+### Creating Nixlets
+Nixlets need a `default.nix` and a `values.nix` (a `nixlet.nix` containing the metadata is also recommended). \
 Check out the existing [nixlets](./nixlets/) to understand how they work. \
-There is also a bare bones [template](./template/).
+There is also a bare-bones [template](./template/).
+
+### Using/rendering Nixlets
+To render nixlets you only need to import the nixlets-lib:
+```nix
+{
+  inputs.nixlet-lib.url = "gitlab:TECHNOFAB/nixlets?dir=lib";
+}
+```
+
+#### Nixlets stored in the Gitlab Package Registry
+```nix
+(nixlet-lib.fetchNixletFromGitlab {
+  project = "TECHNOFAB/nixlets";
+  name = "<nixlet>";
+  version = "<version>";
+  sha256 = "<sha>";
+}).render {
+  inherit system;
+  # values = {};
+  # project = "";
+  # overrides = ({...}: {});
+}
+```
+
+#### Nixlets fetchable from arbitrary URLs
+```nix
+(nixlet-lib.fetchNixlet "<URL>" "<sha>").render {
+  # ...
+}
+```
+
+#### Metadata
+Metadata of the Nixlets can also easily be accessed if needed:
+```nix
+(<some nixlet>).description # version, name, etc.
+```