tgpu-cli: Options for output

[iwoplaza]

--input A file or a glob, pointing at .wgsl files to generate JavaScript code from.
--output A file or a pattern that points to where files should be generated (and their extension).

Example inputs & outputs:

• -i file.wgsl -o file.ts - a single file, meaning only a single file as input is permitted. TypeScript code will be generated.
• -i "./**/*.wgsl" -o "*.js" - The wildcard * will be replaced with the extensionless input filename. JavaScript code will be generated.
• -i "./**/*.wgsl" -o "./output/*.ts" - All output files will be placed in ./output/, relative to the CWD of running the script. Any hierarchy in the input files will be flattened.
• -i "./src/**/*.wgsl" -o "./output/**/*.ts" - All output files will be placed in ./output/, relative to the CWD of running the script. The hierarchy in the input files will be kept, relative to ./src/