Identify global Vue components used by the template

[akaptur]

Currently, the explorer only look at the script part of a Vue single file component. If globally-registered Vue components are used in the template, they'll be missed. We could parse the template section in order to support global components as well.

(I'm not sure how difficult this will be. The key part is finding a good parsing tool for Vue templates. Vue itself might be the easiest way forward, since the Vue framework definitionally has solved this problem.)