Add xled, xray, xshape and Comma to Tools

[anderix]

Adding four CSV tools from Excelano to the Tools section:

• xled — sed and awk for CSV: awk's field model and sed's s/// substitution over Excel-style column and row ranges, with a live preview before writing.
• xray — a read-only profiler that reports a CSV's shape, column contents, and likely problems before you clean or query it.
• xshape — geometry-only reshaping: pivot, unpivot, split, merge, transpose, without changing, filtering, or aggregating any value.
• Comma — a native GNOME desktop editor for Linux that saves a delimited file back byte-for-byte, leaving untouched rows unchanged.

Each links to its home page with docs and install instructions. Entries follow the existing - [Name](url) - Description. format and are appended to the end of the Tools list.