[VRL Playground] Separate JS/resources files from WASM generated files

[pront]

In lib/vector-vrl/web-playground/public there is a mix of handwritten and generated files.

Specifically wasm-pack build generates the following files:

README.md
vector_vrl_web_playground.d.ts
vector_vrl_web_playground_bg.wasm
package.json
vector_vrl_web_playground.js
vector_vrl_web_playground_bg.wasm.d.ts

Also, the wasm-pack build --target web --out-dir public command will also generate a .gitignore file that contains a single * so it requires manually editing before committing since we cannot exclude everything.

It would be cleaner to separate the above files and ensure that the build command generates a folder that doesn't need to be committed to the repo.