Test the component using `vue-test-utils`

[vencho-mdp]

I'm submitting a ...

• [ ] bug report
• [x] feature request
• [ ] support request

What is the current behavior?

Component is not tested and it should be, mainly for production usage

How are you importing Vue-simple-suggest?

• [ ] ESNext (original code, single-file .vue component, css included) (import VueSimpleSuggest from 'vue-simple-suggest/lib')
• [x] ES6 (import VueSimpleSuggest from 'vue-simple-suggest')
• [ ] ES7 and above (import VueSimpleSuggest from 'vue-simple-suggest/dist/es7')
• [ ] Bundled version (import VueSimpleSuggest from 'vue-simple-suggest')
• [ ] CommonJS (const VueSimpleSuggest = require('vue-simple-suggest'))
• [ ] UMD Component (<script type="text/javascript" src="https://unpkg.com/vue-simple-suggest"></script>)

What is the motivation / use case for changing the behavior?

Production Usage

Please tell us about your environment:

• Vue.js Version: 2.6
• Vue-simple-suggest version: 1.11
• Browser: [Chrome 98]
• Language: [ES6/7]