Add support for Source modules/functions to HTML Chapter

[zhaojj2209]

Currently, code written in the HTML chapter is unable to make use of Source modules and pre-declared functions. This is because the <iframe> component used to render the HTML code is sandboxed for security issues, making it difficult for code rendered within the <iframe> to access information externally (e.g. info on modules). More research is needed in order to find a way for HTML code to access such information.

For pre-declared functions, one possible way to add support would be to scan the code for any pre-declared functions used, then attach the code for the pre-declared functions to the code as scripts. This would work for simple stand-alone functions, but more work would be needed to allow usage of large libraries (e.g. pairs/lists).

Currently cannot think of a good way to enable module support, especially given that the modules library structure is still evolving. The feasibility of modules support can be examined once the modules library structure has more or less stabilised.

[leeyi45]

I've briefly thought about this, and this can probably be done since most browsers support dynamic import() calls. The issue, however, lies with the fact that there's no way for the HTML code to access the context.