Improve string substitution in the worker file

[jtpio]

Currently there is a build step in package.json involving a call to sed to replace a substring:

xeus-lua-kernel/package.json

Line 45 in e3a1937

"sed-worker": "shx sed -i \"s/XEUS_KERNEL_FILE/'.\\/xlua_wasm.js'/\" src/worker.ts && shx sed -i \"s/LANGUAGE_DATA_FILE/''/\" src/worker.ts ",

We should look into making this step more robust.

[JohanMabille]

A solution suggested by @jtpio is to use handlebars.
Another solution would be to have the ts files generated / confugred by cmake when building the jupyterlite kernels.