feat(parser): add comment_lines option to skip header metadata lines

[hat0uma]

Summary

• Add new comment_lines parser option that treats the first N lines as comments regardless of content
• Useful for CSV files with fixed header/metadata sections (e.g., file info, creation date)
• Can be combined with existing comments prefix detection

Changes

• Add comment_lines option to CsvView.Options.Parser
• Create util.create_is_comment(opts) function to unify comment detection logic
• Refactor parser to accept comment detection function instead of comment prefixes
• Update sniffer to use the new comment detection approach

Usage

-- In setup
require('csvview').setup({
parser = {
  comment_lines = 2,  -- Skip first 2 lines as metadata
}
})

-- Or via command line
:CsvViewEnable comment_lines=2

Example:

File: data.csv
Created: 2024-01-01
name,age,city
John,25,New York

Setting comment_lines = 2 will treat the first two lines as comments and parse from line 3.

Close #83