update readme

Author: Gozala

Readme.md

@@ -1,36 +1,48 @@
 # random-access-idb-mutable-file
+
 [![travis][travis.icon]][travis.url]
 [![package][version.icon] ![downloads][downloads.icon]][package.url]
 [![styled with prettier][prettier.icon]][prettier.url]
 
+[random-access][random-access-storage] storage layer over [IDBMutableFile][], which is **non-standard** IndexedDB extension in Gecko to provide virtual file system API with-in the IndexedDB.
 
-
-random-access-storage provider via non-standard IDBMutableFile API
+This library will only work in Firefox (unless other browsers implement [IDBMutableFile][] API) and it's mostly targeted at [WebExtensions][]. It mostly amis to be a drop-in replacement for [random-access-file][]. It is also an alternative to [random-access-idb][] that is able to avoid loading all of the file content for random read / writes at the expanse of limited runtime suport.
 
 ## Usage
 
-### Import
-
-Rest of the the document & provided code examples assumes that library is installed (with yarn or npm) and imported as follows:
-
 ```js
-import * as random-access-idb-mutable-file from "random-access-idb-mutable-file"
+import RandomAccess from "random-access-idb-mutable-file"
+
+const main = async (filename, options) => {
+  const randomAccessFile = await RandomAccess.mount()
+
+  const file = randomAccessFile(filename, options)
+  file.write(10, Buffer.from("hello"), error => {
+    // write a buffer to offset 10
+    file.read(10, 5, (error, buffer) => {
+      console.log(buffer) // read 5 bytes from offset 10
+      file.close(() => {
+        console.log("file is closed")
+      })
+    })
+  })
+}
 ```
 
-
-
 ## Install
 
     npm install random-access-idb-mutable-file
 
 [travis.icon]: https://travis-ci.org/Gozala/random-access-idb-mutable-file.svg?branch=master
 [travis.url]: https://travis-ci.org/Gozala/random-access-idb-mutable-file
-
 [version.icon]: https://img.shields.io/npm/v/random-access-idb-mutable-file.svg
 [package.url]: https://npmjs.org/package/random-access-idb-mutable-file
-
 [downloads.icon]: https://img.shields.io/npm/dm/random-access-idb-mutable-file.svg
 [downloads.url]: https://npmjs.org/package/random-access-idb-mutable-file
-
-[prettier.icon]:https://img.shields.io/badge/styled_with-prettier-ff69b4.svg
-[prettier.url]:https://github.com/prettier/prettier
+[prettier.icon]: https://img.shields.io/badge/styled_with-prettier-ff69b4.svg
+[prettier.url]: https://github.com/prettier/prettier
+[random-access-storage]: https://github.com/random-access-storage/random-access-storage
+[random-access-file]: https://github.com/random-access-storage/random-access-file
+[idbmutablefile]: https://developer.mozilla.org/en-US/docs/Web/API/IDBMutableFile
+[webextensions]: https://developer.mozilla.org/en-US/Add-ons/WebExtensions
+[random-access-idb]: https://github.com/random-access-storage/random-access-idb