Adds additional characters with multiple entry points

[dfbaskin]

When multiple entry points are found (like when using web workers), then extra comma (',') characters get written to the html file. The injection code needs to expand the bundles array, something like this:

// Inject the script tags before the body close tag
const injected = [
    tmpl.slice(0, bodyCloseTag),
    ...bundles.map(b => `<script src="${b}"></script>\n`),
    tmpl.slice(bodyCloseTag, tmpl.length),
].join("");