Update Emscripten version, at least for manual compilation #89
Description
Potential benefits:
- Better performance
- Smaller output files
- Improved debugging
- Modern JavaScript features
- Better WASM support
Potential risks are that Emscripten upgrades can introduce breaking changes in:
- Build flags and syntax
- WASM/ASM.js output format
- Runtime behavior
- Library compatibility
Additionally, it would be necessary to synchronize the Emscripten version used in kiwix/kiwix-build (or openzim/libzim, not sure which).