investigate ways to load additional data on demand

Coming from #3524.

xterm.js currently has no way to load additional data on demand in the core. We are at “either it is there prebundled - or forget it”.

We should investigate, how we can externalize rarely used (blob) data into additional resources, that can be requested on demand. Ideally things cover these aspects:

• easy to use in code
• either works transparently with TS’ import statement, or does not interfere negatively
• keep working for CJS/ESM
• keeps working in nodejs and browser context
• support proper electron bundling
• keep working with common web bundlers (webpack, Rollup, parcel …)

Sidenote: JSON imports are working for most above, but not all - like ESM currently cannot handle it. A workaround to that might be to use the ESM import() function at code level with real JS modules (JSON data written to proper code units). Needs investigation…

[Eugeny]

IMO dynimport looks good, but users should be able to override the implementation.

Points to consider:

• Path format passed to dynimport()
• Whether two separate builds (with statically bundled resources and without) are necessary
• Fallback in case a user chooses not to provide the JSON files at all (i.e. disable named color support in #3524)
• If JS imports are coming in the future, whether we have to mandate the packaging format for these

[jerch]

Out of scope, thus closing.