Update README.md

[tomterl]

serde-0.9 no longer has this bug;
testing lsd with a zero-byte colors.yaml works just fine showing the default theme.

---

TODO

• Use cargo fmt
• Add necessary tests
• Update default config/theme in README (if applicable)
• Update man page at lsd/doc/lsd.md (if applicable)

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[tomterl]

This is a readme only change - how important/possible are the standard todos above?

[zwpaper]

hi @tomterl, good catch! it's ok to ignore them for a doc update