Add pool documentation

Author: Kikobeats

README.md

@@ -102,11 +102,32 @@ An incognito page will not share cookies/cache with other browser pages.
 
 ### .pool(options)
 
-Tha main **browserless** constructor expose a singleton browser. This is enough for most scenarios, but in case you need you can intialize a **pool of instances**.
+**browserless** uses internally a singletion browser instance.
+
+You can use `.pool` constructor for creating a **pool of instances**:
 
 ```js
 const createBrowserless = require('browserless')
-const browserless = createBrowserless.pool()
+const browserlessPool = createBrowserless.pool()
+```
+
+After that, the API is the same. The acquire/release is done automagically.
+
+You can interact with a **browserless** instance directly as well:  
+
+```js
+const createBrowserless = require('browserless')
+const browserlessPool = createBrowserless.pool()
+
+// get a browserless instance from the pool
+browserlessPool(async browserless => {
+  // get a page from the browser instance
+  const page = await browserless.page()
+  await browserless.goto(page, { url: url.toString() })
+  const html = await page.content()
+  console.log(html)
+  process.exit()
+})
 ```
 
 #### options

examples/pool.js

@@ -0,0 +1,17 @@
+'use strict'
+
+const createBrowserless = require('..')
+const browserlessPool = createBrowserless.pool()
+
+const url = new URL(process.argv[2])
+;(async () => {
+  // get a browserless instance from the pool
+  browserlessPool(async browserless => {
+    // get a page from the browser instance
+    const page = await browserless.page()
+    await browserless.goto(page, { url: url.toString() })
+    const html = await page.content()
+    console.log(html)
+    process.exit()
+  })
+})()

src/pool/index.js

@@ -11,8 +11,7 @@ module.exports = ({ opts, ...launchOpts } = {}) => {
   const poolOpts = { ...POOL_OPTS, ...opts }
   const pool = createPool(poolOpts, launchOpts)
   ;['html', 'text', 'pdf', 'screenshot'].forEach(key => {
-    pool[key] = (url, opts) =>
-      pool.use(browserless => browserless[key](url, opts))
+    pool[key] = (url, opts) => pool(browserless => browserless[key](url, opts))
   })
   return pool
 }