Store and load EPub from local storage

[M0nica]

• Add support to extract Manifest information from remote container.xml and *.opf urls.
• Save exploded EPubs to local storage and render in webpub-viewer from local storage in order to render remote EPubs in IFrame without CORS issues.
• Images are rendered by rewriting XHTML files in localstorage to use base64 encoded version from local storage.
• Temporarily CSS is being pulled from remote URL. This, in addition to asset handling will be revisited in future work.

It pulled in all the commits from https://github.com/NYPL-Simplified/webpub-viewer/tree/testingExplodedEPubs since I based this branch off of that one 🤯

Screenshot of how localhost files are saved in localstorage (it's the same structure for the remote files as well but the key has the remote URL instead)