Avoid rendering duplicate Vue-related script elements on book pages

[jimchamp]

Closes #8493

The render_component function, when called for the first time, appends a script element which pulls in Vue. It also renders a script element for the specific component the first time that component is rendered on a page.

The first time that render_component is called on the book page is in the edition/modal_links template. Prior to these code changes, the rendered modal links were stored in a variable which was rendered twice in databarWork.html, resulting in duplicate script tags.

Since rendering the edition/modal_links template takes very little time, render_template is now called both times the modal links are rendered.

Technical

Testing

Screenshot

Stakeholders

[cdrini]

Nice lgtm! Testing on testing.openlibrary.org . The modal opens, works like a charm, and doesn't load vue twice!