inbox: add health endpoint & docs (#64)

* inbox: add health endpoint && docs

* inbox: update post endpoint uri

* inbox: update docs & dockerfile

---------

Co-authored-by: Abdullah Atta <abdullahatta@streetwriters.co>

Notesnook.Inbox.API/README.md

@@ -0,0 +1,68 @@
+# Notesnook Inbox API
+
+## Running locally
+
+### Requirements
+
+- Bun (v1.3.0 or higher)
+
+### Commands
+
+- `bun install` - Install dependencies
+- `bun run dev` - Start the development server
+- `bun run build` - Build the project for production
+- `bun run start` - Start the production server
+
+## Self-hosting
+
+The easiest way to self-host is with Docker or Docker Compose.
+
+Prerequisites:
+
+- `docker` (Engine) installed
+- `docker-compose` (optional, for multi-service setups)
+
+Build and run with Docker:
+
+```bash
+# build the image from the current folder
+docker build -t notesnook-inbox-api .
+
+# run the container (example)
+docker run --rm -p 3000:3000 \
+	-e PORT=3000 \
+	-e NOTESNOOK_API_SERVER_URL="https://api.notesnook.com" \
+	notesnook-inbox-api
+```
+
+Docker Compose (example):
+
+```yaml
+services:
+	inbox-api:
+		image: notesnook-inbox-api
+		build: .
+		ports:
+			- "3000:3000"
+		environment:
+			PORT: 3000
+			NOTESNOOK_API_SERVER_URL: "https://api.notesnook.com"
+		restart: unless-stopped
+```
+
+Environment variables:
+
+- `PORT` — port the service listens on (default: `5181`)
+- `NOTESNOOK_API_SERVER_URL` — base URL of the Notesnook API used to fetch public inbox keys
+
+_If you prefer running without Docker, use `bun install` and `bun run start` with the environment variables set._
+
+## Writing from scratch
+
+The inbox API server is pretty simple to write from scratch in any programming language and/or framework. There's only one endpoint that needs to be implemented, which does these three steps:
+
+1. Fetch the user's public inbox API key from the Notesnook API.
+2. Encrypt the payload using `openpgp` or any other `openpgp` compatible library.
+3. Post the encrypted payload to the Notesnook API.
+
+You can refer to the [source code](./src/index.ts) for implementation details.