feat(text): add Line Filter tool

[punch-github]

Summary

Adds a new Line Filter tool to the Text group. Given a block of text, it keeps (or excludes) lines that match a pattern — useful for grep-style filtering of logs, CSVs, configs, etc.

Features

• Three match modes:
  • Plain text — substring match
  • Keywords (any) — whitespace-separated keywords; a line is kept when it contains any of them
  • Regular expression — full .NET regex with a 2-second timeout
• Case-sensitive toggle
• Invert match toggle (keep vs. exclude matching lines)
• Live preview of filtered output
• Match summary — Matched X of Y lines
• Yellow highlights of pattern occurrences in the input pane
• Pattern row stays pinned at the top while the output pane is extended
• Friendly error InfoBar for invalid regex
• Loading from a file is handled by the built-in multi-line-input toolbar (no extra UI needed)

Screenshot

Files added

• src/DevToys.Tools/Tools/Text/LineFilter/LineFilterGuiTool.cs
• src/DevToys.Tools/Tools/Text/LineFilter/LineFilter.resx
• src/DevToys.Tools/Tools/Text/LineFilter/LineFilter.Designer.cs
• docs/screenshots/line-filter-keywords.png

Notes for reviewers

• Only the English .resx is included; happy to follow up with the locale resx fan-out (or rely on the existing Crowdin pipeline) — please advise.
• Icon uses FluentSystemIcons glyph \uF211. Happy to swap for a custom DevToys-Tools-Icons glyph if preferred.
• Builds cleanly against DevToys.Tools.csproj; only pre-existing warnings remain (none from new files).

Testing

• Verified end-to-end inside the DevToys host (Windows) using a local plugin build of DevToys.Tools.dll:
  • Plain text, Keywords, and Regex modes — all match, highlight, and summary correctly.
  • Case-sensitive toggle behaves as expected in all three modes.
  • Invert match excludes the right lines (highlights still mark the would-be matches in the input).
  • Invalid regex shows the InfoBar without breaking the UI.

[punch-github]

This PR addresses the issue DevToys-app/DevToys#1676