renderer: add wrapLines option for line-by-line and side-by-side views

Introduce a new `wrapLines` configuration option that enables word-wrap
display for diff output. When enabled, lines wrap at the container
boundary instead of overflowing horizontally.

Changes:
- Add `wrapLines` boolean config to render-utils, line-by-line-renderer,
  side-by-side-renderer, and diff2html default config
- Refactor mustache templates to separate row wrapping (generic-line)
  from cell content (generic-line-content), enabling flexible composition
- Apply `d2h-wrapped-file-diff` CSS class conditionally to activate
  word-break and white-space styles scoped to wrapped mode only
- Fix side-by-side view to render an aligned empty header row on the
  right panel so context lines are not visually offset
- Add wrapLines checkbox to the demo page UI
- Update test snapshots to reflect new template structure

Author: mohanapriyac9691