fix README, and add logo

README.md

@@ -1,11 +1,16 @@
 # go-cache
 
+[![GoDev](https://img.shields.io/badge/go.dev-doc-007d9c?style=flat-square&logo=read-the-docs)](https://pkg.go.dev/github.com/viney-shih/go-cache?tab=doc)
 [![Build Status](https://app.travis-ci.com/viney-shih/go-cache.svg?branch=master)](https://app.travis-ci.com/viney-shih/go-cache)
 [![Go Report Card](https://goreportcard.com/badge/github.com/viney-shih/go-cache)](https://goreportcard.com/report/github.com/viney-shih/go-cache)
 [![codecov](https://codecov.io/gh/viney-shih/go-cache/branch/master/graph/badge.svg?token=QKRiNSU5Gn)](https://codecov.io/gh/viney-shih/go-cache)
 [![Coverage Status](https://coveralls.io/repos/github/viney-shih/go-cache/badge.svg?branch=master)](https://coveralls.io/github/viney-shih/go-cache?branch=master)
 [![License](http:https://img.shields.io/badge/License-Apache_2-red.svg?style=flat)](http:https://www.apache.org/licenses/LICENSE-2.0)
 
+<p align="center">
+ <img src="assets/logo.png" title="viney-shih/go-cache" />
+ <span>Photo by <a href="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/ashleymcnamara">Ashley McNamara</a>, via <a href="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/ashleymcnamara/gophers">ashleymcnamara/gophers</a> (CC BY-NC-SA 4.0)</span>
+</p>
 
 A library of mixed version of **key:value** store interacts with private (in-memory) cache and shared cache (i.e. Redis) in Go. It provides `Cache-Aside` strategy when dealing with both, and maintains the consistency of private cache between distributed systems by `Pub-Sub` pattern.