Make vue-template-compiler a peerDependency

[abrenneke]

Requiring require-extension-hooks-vue errors if the vue-template-compiler version doesn't match the imported version of Vue.

For example, as this currently depends on "^2.5.17", and I upgraded to Vue 2.6.9, I get the following error:

Error:

Vue packages version mismatch:

- vue@2.6.9
- vue-template-compiler@2.5.17

This may cause things to work incorrectly. Make sure to use the same version for both.
If you are using vue-loader@>=10.0, simply update vue-template-compiler.
If you are using vue-loader@<10.0 or vueify, re-installing vue-loader/vueify should bump vue-template-compiler to the latest.

    at Object.<anonymous> (/code/work/cms2/node_modules/require-extension-hooks-vue/node_modules/vue-template-compiler/index.js:8:9)

I think making vue-template-compiler a peerDependency solves the issue, but maybe there's a better way.

[abrenneke]

I see that @dhershman1 upgraded vue-template-compiler in #34. It would be nice if this package didn't have to upgrade when Vue was upgraded, but it's also annoying for projects to have to include vue-template-compiler themselves in devDependencies. Maybe there's a best of both worlds somehow?