Feat: Implement test suite

[ndrscodes]

adds unit tests. tests added:

• Uses a custom webpack compiler in order to check if a valid template is created
• Uses a custom webpack compiler in order to test if vue-loader is able to compile the template generated by the loader
• checks if the loader yields the same result when invoked by webpack and when called directly
• checks if the loader injects a v-on directive into the svg tag if Vue 2 is detected