jless: add page

[mvanhorn]

Adds a tldr page for jless, a command-line JSON viewer with vim-style navigation.

Covers: viewing JSON files, piping from stdin, YAML mode, line mode for JSONL, and initial search query.

Documentation: https://jless.io/user-guide

Fixes #21116

This contribution was developed with AI assistance (Claude Code).

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[tldr-bot]

The build for this PR failed with the following error(s) at commit
f1bd7829db44d56636e1a229f9065df304efb28b:

pages/common/jless.md:10: TLDR112 Term `stdin` should be lowercase and wrapped in backticks (`stdin`)

Please fix the error(s) and push again.