Rule proposal: `vue/prefer-separate-static-class`

[FloEdelmann]

Please describe what the rule should do:
Report static classes in bound class attributes.

What category should the rule belong to?
[x] Enforces code style (layout)
[ ] Warns about a potential error (problem)
[ ] Suggests an alternate way of doing something (suggestion)
[ ] Other (please specify:)

Provide 2-3 code examples that this rule should warn about:

<!-- FAIL -->
<div v-bind:class="'static-class'" />
<div :class="'static-class'" />
<div :class="`static-class`" />
<div :class='"static-class"' />
<div :class="['static-class']" />
<div :class="[`static-class`]" />
<div :class='["static-class"]' />
<div :class="{'static-class': true}" />
<div :class="{foo: true}" />
<div :class='{"static-class": true}' />
<div :class="{['static-class']: true}" />
<div :class="{[`static-class`]: true}" />
<div :class="[{'static-class': true}]" />

<div :class="['static-class', dynamicClass]" />
<div :class="{'static-class': true, 'dynamic-class': foo}" />

<!-- PASS -->
<div class="static-class" />
<div :class="dynamicClass" />
<div class="static-class" :class="dynamicClass" />
<div class="static-class" :class="[dynamicClass]" />
<div class="static-class" :class="{'dynamic-class': foo}" />>

[ota-meshi]

I like that rule 👍