Poor embed load performance (loaded serially, should be in parallel)

[jhildenbiddle]

Docsify embeds are loaded serially instead of in parallel. This has a significant performance impact on pages that have more than one embed.

Take the Customization page of the docsify-themeable site as an example.

This page loads ten separate embeds for a combined total of roughly 12k. Despite the light payload, the embeds take six seconds to load as a result of loading them serially. Load performance would be dramatically improved if these files were loaded in parallel.

[jhildenbiddle]

Thank you! 🎉