Add content loader for json-lines and ztsd, gzip and zlib encoding

[jeparlefrancais]

Closes #353

Adds new content loaders and encoding options for embedding file content.

• json_lines loader to support line-delimited json
• compression encodings zstd, gzip and zlib: new variants for string, buffer, and bytes loaders

Just like the existing base64, the content is compressed at build time by darklua and embedded as-is. Decoding is left to the runtime.

• add entry to the changelog
• update docs

[github-actions]

Coverage after merging json-lines-content-loader into main will be

84.92%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/frontend
configuration.rs	82.26%	100%	80.60%	82.55%	114–117, 121–125, 129–132, 136–140, 143–146, 149–154, 157–159, 241–260, 262–263, 345–349, 81–83, 94–97
content_loader.rs	67.88%	100%	47.37%	70.11%	113–116, 118–120, 123–125, 245–247, 287, 294–295, 315–317, 334–335, 337–339, 341, 344–347, 349–352, 354, 357–360, 362–365