docs: list all options

Author: darrachequesne

README.md

@@ -25,6 +25,128 @@ io.on("connection", (socket) => {
 });
 ```
 
+## Options
+
+### `path`
+
+Default value: `/engine.io/`
+
+It is the name of the path that is captured on the server side.
+
+Caution! The server and the client values must match (unless you are using a
+path-rewriting proxy in between).
+
+Example:
+
+```ts
+const engine = new Server(httpServer, {
+  path: "/my-custom-path/",
+});
+```
+
+### `pingTimeout`
+
+Default value: `20000`
+
+This value is used in the heartbeat mechanism, which periodically checks if the
+connection is still alive between the server and the client.
+
+The server sends a ping, and if the client does not answer with a pong within
+`pingTimeout` ms, the server considers that the connection is closed.
+
+Similarly, if the client does not receive a ping from the server within
+`pingInterval + pingTimeout` ms, the client also considers that the connection
+is closed.
+
+### `pingInterval`
+
+Default value: `25000`
+
+See [`pingTimeout`](#pingtimeout) for more explanation.
+
+### `upgradeTimeout`
+
+Default value: `10000`
+
+This is the delay in milliseconds before an uncompleted transport upgrade is
+cancelled.
+
+### `maxHttpBufferSize`
+
+Default value: `1e6` (1 MB)
+
+This defines how many bytes a single message can be, before closing the socket.
+You may increase or decrease this value depending on your needs.
+
+### `allowRequest`
+
+Default value: `-`
+
+A function that receives a given handshake or upgrade request as its first
+parameter, and can decide whether to continue or not.
+
+Example:
+
+```ts
+const engine = new Server({
+  allowRequest: (req, connInfo) => {
+    return Promise.reject("thou shall not pass");
+  },
+});
+```
+
+### `cors`
+
+Default value: `-`
+
+A set of options related to
+[Cross-Origin Resource Sharing](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS)
+(CORS).
+
+Example:
+
+```ts
+const engine = new Server({
+  cors: {
+    origin: ["https://example.com"],
+    allowedHeaders: ["my-header"],
+    credentials: true,
+  },
+});
+```
+
+### `editHandshakeHeaders`
+
+Default value: `-`
+
+A function that allows to edit the response headers of the handshake request.
+
+Example:
+
+```ts
+const engine = new Server({
+  editHandshakeHeaders: (responseHeaders, req, connInfo) => {
+    responseHeaders.set("set-cookie", "sid=1234");
+  },
+});
+```
+
+### `editResponseHeaders`
+
+Default value: `-`
+
+A function that allows to edit the response headers of all requests.
+
+Example:
+
+```ts
+const engine = new Server({
+  editResponseHeaders: (responseHeaders, req, connInfo) => {
+    responseHeaders.set("my-header", "abcd");
+  },
+});
+```
+
 ## License
 
 [MIT](/LICENSE)