docs: improve readme file

Author: nodkz

README.md

@@ -8,6 +8,75 @@
 
 This is a plugin for [graphql-compose](https://github.com/graphql-compose/graphql-compose), which generates GraphQLTypes for [bullmq](https://github.com/taskforcesh/bullmq).
 
+## Installation
+
+```bash
+npm install graphql graphql-compose bullmq graphql-compose-bullmq --save
+```
+
+Modules `graphql`, `graphql-compose`, `bullmq` are in `peerDependencies`, so should be installed explicitly in your app. They have global objects and should not have ability to be installed as submodule.
+
+## Example
+
+```js
+import { composeBull } from 'graphql-compose-bullmq';
+import { schemaComposer } from 'graphql-compose';
+
+const { queryFields, mutationFields } = composeBull({
+  schemaComposer,
+  typePrefix: 'Prefix',
+  jobDataTC: `type MyJobData { fieldA: String! fieldB: String}`,
+  queue: {
+    name: 'fetch_metrics',
+    prefix: 'bull.demo',
+  },
+  redis: 'redis://127.0.0.1:6379',
+});
+
+schemaComposer.Query.addFields({
+  ...queryFields,
+  // Will provide the following fields:
+  //   queueKeys
+  //   queues
+  //   queue
+  //   job
+});
+
+schemaComposer.Mutation.addFields({
+  ...mutationFields,
+  // Will provide the following fields:
+  //   queueClean
+  //   queueDrain
+  //   queuePause
+  //   queueResume
+  //   queueRemoveRepeatable
+  //   jobAdd
+  //   jobAddBulk
+  //   jobAddRepeatableCron
+  //   jobAddRepeatableEvery
+  //   jobDiscard
+  //   jobPromote
+  //   jobRemove
+  //   jobRetry
+  //   jobUpdate
+  //   jobLogAdd
+});
+
+const schema = schemaComposer.buildSchema();
+```
+
+## Schema
+
+`composeBull` will generate particles for your further schema. It contains more than 40 types wich helps to you work with Bull Queues. You may see generated files in [schema.graphql](./example/schema.graphql) file. It can be visialized with <https://apis.guru/graphql-voyager/> in the following manner:
+
+### Queries
+
+<img width="1323" alt="Screen Shot 2020-04-14 at 21 22 38" src="https://user-images.githubusercontent.com/1946920/79242603-5ab18900-7e96-11ea-8aad-7aff95e285ba.png">
+
+### Mutations
+
+<img width="1327" alt="Screen Shot 2020-04-14 at 21 24 05" src="https://user-images.githubusercontent.com/1946920/79242633-61d89700-7e96-11ea-9efc-3afadc3e082c.png">
+
 ## License
 
 [MIT](https://github.com/graphql-compose/graphql-compose-bullmq/blob/master/LICENSE.md)