Add --format flag for JSON and CSV output

[AshayK003]

## Description

New --format / -f flag for the search command, supporting three output formats:

Format	Behavior
table	Existing fancy_grid tabulate output (default)
json	Pretty-printed array of {title, url} — pipe into jq or other tools
csv	Standard CSV with Title,Issue URL headers — open in spreadsheets

All formats print the remaining rate limit and "Happy Hacking" footer afterward.

Example

Testing

pytest tests/ — 19 passed
ruff check . — clean

[AshayK003]

@maintainers Bumping this one \u2014 adds a --format flag for JSON/CSV output to the CLI. Useful for scripting and automation. Happy to make changes if needed.

[yankeexe]

@AshayK003 Can you please add a screenshot of this working?

[AshayK003]

All three output formats working with --format / -f:

Search: gfi search "AshayK003" --user --limit 3

Format	Command	Output
table (default)	(no flag)	Existing fancy_grid tabulate — unchanged
json	--format json / -f json	Pretty-printed [{title, url}] — pipeable into jq
csv	--format csv / -f csv	Standard CSV with Title,Issue URL headers

Rate-limit footer and "Happy Hacking" message print consistently across all three formats.

[yankeexe]

@AshayK003 please add the screenshot on the Pull Request description, not as a part of the change.

[AshayK003]

@AshayK003 please add the screenshot on the Pull Request description, not as a part of the change.
Done.