📘 doc: add mobius mention to graphql yoga

Author: SaltyAom

docs/plugins/graphql-yoga.md

@@ -52,6 +52,39 @@ optional: you can install custom version of optional peer dependencies as well:
 bun add graphql graphql-yoga
 ```
 
+## Resolver
+Elysia use [Mobius](https://github.com/saltyaom/mobius) to infers type from **typeDefs** field automatically, allowing you to get full type-safety and auto-complete when typing **resolver** types.
+
+## Context
+You can add custom context to resolver function by adding **context**
+```ts
+import { Elysia } from 'elysia'
+import { yoga } from '@elysiajs/graphql-yoga'
+
+const app = new Elysia()
+    .use(
+        yoga({
+            typeDefs: /* GraphQL */`
+                type Query {
+                    hi: String
+                }
+            `,
+            context: {
+                name: 'Mobius'
+            },
+            // If context is a function on this doesn't present
+            // for some reason it won't infer context type
+            useContext(_) {}
+            resolvers: {
+                Query: {
+                    hi: async (parent, args, context) => context.name
+                }
+            }
+        })
+    )
+    .listen(8080)
+```
+
 ## Config
 This plugin extends [GraphQL Yoga's createYoga options, please refers to the GraphQL Yoga documentation](https://the-guild.dev/graphql/yoga-server/docs) with inlining `schema` config to root.