Add `Vue.extend` as valid component rule trigger

[blake-newman]

All component-related rules are being applied to code that passes any of the following checks:

• Vue.component() expression
• export default {} in .vue or .jsx file

Suggestion

Add Vue.extend to the triggers for for applying the component related rules. It is a commonly used api fo creating components in a raw formats without SFC.

[michalsnik]

Good idea @blake-newman On it :)

[blake-newman]

Nice, cheers. Was doing it myself you beat me to it.