JS Browser sourcemap support | net::ERR_FILE_NOT_FOUND
### Description

How do you run/debug your code? I'm unable to generate source maps. Are there any examples of browser setups where source maps are compiled with relative paths, and "nim" files are output to a build folder? 

This method https://github.com/nim-lang/vscode-nim/blob/b5bc39cddbd69b858481bcc6d1e8d18f0f9bae85/nimvscode.nimble#L27C10-L27C92 generates source maps with absolute paths. I'm looking for relative paths. Manually changing the "urls" in the "build.js.map" somewhat works, but the problem lies in Nim source code like "compilation.nim".

### Nim Version

Nim Compiler Version 2.0.8 [Windows: amd64]
Compiled at 2024-07-03
Copyright (c) 2006-2023 by Andreas Rumpf

active boot switches: -d:release

### Current Output

```text
# nim js -d:release -d:danger --outdir:out --checks:off --sourceMap src/main.nim

# src/main.nim
import std/jsffi
func log(arg, arg2: SomeNumber) {.importjs: """console.log(#, #)""".}
log(42, 9)

# out/main.js.map
{"version":3,"sources":["C:\\Users\\kauder\\.choosenim\\toolchains\\nim-2.0.8\\lib\\system\\compilation.nim","C:\\Users\\kauder\\.choosenim\\toolchains\\nim-2.0.8\\lib\\pure\\hashes.nim","C:\\Users\\kauder\\.choosenim\\toolchains\\nim-2.0.8\\lib\\js\\jsffi.nim","C:\\Users\\kauder\\Documents\\installer\\Github\\playground\\nim\\probe_js\\src\\main.nim"],"names":["objectID"],"mappings":";;;;AAiBI;ACwME;AAAA,IAAAA;AC7KJ;AACA;ACzCC;AAAA;AAAA;","file":"C:\\Users\\kauder\\Documents\\nim\\probe_js\\out\\main.js"}
```


### Expected Output

```text
{"version":3,"sources":["probe_js\\nim-2.0.8\\lib\\system\\compilation.nim","probe_js\\nim-2.0.8\\lib\\pure\\hashes.nim","probe_js\\nim-2.0.8\\lib\\js\\jsffi.nim","probe_js\\src\\main.nim"],"names":["objectID"],"mappings":";;;;AAiBI;ACwME;AAAA,IAAAA;AC7KJ;AACA;ACzCC;AAAA;AAAA;","file":"probe_js\\out\\main.js"}
```


### Possible Solution

Copy nim source files along with the build file and change to relative paths in the output.js.map sources.


### Additional Information

Source map failed to load net::ERR_FILE_NOT_FOUND

![image](https://github.com/user-attachments/assets/4384db28-957b-4cfd-863d-29aaa2d3e1d5)
