feat: update readme to include detailed info

Author: acrusella

README.md

@@ -1,3 +1,78 @@
+## How does it work?
+
+It uses Astro Content Collections just like we use `settings.yml`, `content.yml` and `faqs.yml`.
+
+This means every collection is treated as an entrypoint in the CMS.
+
+The necessary config to integrate this is done at `astro.config.mjs`.
+
+## How does config work?
+
+Inside `astro.config.mjs` at `export default defineConfig({ integrations: [...] )}` we need to set:
+
+```
+NetlifyCMS({
+      config: {
+        backend: {
+          name: 'git-gateway',
+          branch: 'master',
+        },
+        collections: [
+            {
+                name: 'Cities',
+                label: 'Cities Content',
+                folder: 'src/content/city',
+                filter: {field: "filter", value: "city"},
+                create: true,
+                delete: true,
+                slug: "{{fields.name}}",
+                fields: [
+                    { name: 'name', widget: 'string', label: 'City Name' },
+                    { name: 'language', widget: 'string', label: 'Language' },
+                    { name: 'info', widget: 'markdown', label: 'City Info' }
+                ],
+            },
+        ],
+      },
+    }),
+
+```
+We can see two main properties, backend and collections. We will take a look the options inside collecitons:
+
+The main options we have to consider are `create: true`, `delete: true` and `slug: "{{fields.name}}"`. Create and Delete properties allow us to enable/disable item creation inside the collection, and slug works just like field summary we have been using in `landings-cms > landing-* > config.json`.
+
+We have also set `filter: {field: "filter", value: "city"}` as a workaround to use nested content-collections which is not a possible option by default. By default we would have needed to set manually all possible collections. Let's see what nested collections can look like:
+
+```
+├── public/
+├── src/
+│   ├── content/
+│       ├── city/
+│           └── en/
+│               └── madrid.md
+│           └── fr/
+│               └── paris.md
+```
+
+Finally, fields property is an array of objects with the default NetlifyCMS options we know `name: ...`, `label: ...` ...
+Be careful to set the same name in fields config to the field in markdown.
+
+## How are new collections created?
+
+If `create: true`, users will be able to add new items inside a collection.
+
+By setting a slug just like mentioned before, we can set field value as file name.
+
+## How are changes made?
+
+This works as expected, the value from the modified field is updated. In workflow by default we have three options:
+
+```
+- Publish now
+- Publish and create new
+- Publish and duplicate
+```
+
 # Astro Netlify-CMS Integration
 
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