docs: readme, contributing [skip ci]

CONTRIBUTING.md

@@ -0,0 +1,5 @@
+# Contributing
+
+Thank you for showing an interest in contributing to Eik 🧡
+
+You can find [the contribution docs here](https://github.com/eik-lib/.github/blob/main/CONTRIBUTING.md).

README.md

@@ -1,3 +1,54 @@
 # @eik/core
 
-Core server functionallity
+This module holds the core server functionality of [`@eik/service`](https://github.com/eik-lib/service#readme).
+Each [HTTP API endpoint](https://eik.dev/docs/server/http-api) has
+its own class handling the specific path and method.
+
+## API
+
+### http
+
+This namespace holds the different HTTP API endpoint handlers. Each handler is a class with an async `handler` method.
+
+```js
+import { http } from "@eik/core";
+
+let pkgGetHandler = new eik.http.PkgGet({ organizations, sink, logger });
+
+let response = await pkgGetHandler.handler(
+	request,
+	type,
+	name,
+	version,
+	extras,
+);
+```
+
+For a more complete usage example, see
+[the implementation in `@eik/service`](https://github.com/eik-lib/service/blob/00c85c1d366df50b688a82e62e5890381df11b0f/lib/main.js#L76-L113).
+
+### prop
+
+A gollection of globals holding base paths.
+
+```js
+import { prop } from "@eik/core";
+
+const { base_auth, base_map, base_pkg, base_npm } = prop;
+```
+
+### HealthCheck
+
+A health check implementation that does a create, read and delete check
+against the configured [storage sink](https://eik.dev/docs/server/storage).
+
+```js
+import { HealthCheck } from "@eik/core";
+
+const health = new HealthCheck({
+	logger,
+	sink,
+});
+
+await health.check();
+```