[Feature] add lines block to display line counts for files

[jeffmylife]

Summary

Adds a new lines block that displays line counts for text files, with support for directory totals when using --total-size.

Motivation

I often want to see line counts when exploring codebases, especially in tree mode. This provides a quick overview of code volume without needing external tools like wc -l.

Example Usage

Basic line counting

lsd --blocks lines,name src/

# Tree mode without totals (directories show "-")
lsd --tree --depth 2 --blocks name,lines,size src/

# Tree mode with totals (directories show cumulative counts)
lsd --tree --depth 2 --blocks name,lines,size --total-size src/

Screenshot

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TODO

• Use cargo fmt
• Add necessary tests
• Update config sample file in doc/samples (if applicable)
• Update man page at lsd/doc/lsd.md (if applicable)

Disclaimer

This is 99% vibe coded with Claude. Feel free to completely disregard this PR and treat this as a detailed feature request.