[docs] Add repository citation metadata via CITATION.cff

[Copilot]

stockplotr did not have repository-level citation metadata, so GitHub and downstream tooling had nothing standardized to surface for attribution. This adds a CITATION.cff aligned with the package’s existing DESCRIPTION metadata.

• Citation metadata

  • Adds CITATION.cff at the repo root
  • Captures package title, version, repository URL, and MIT license
  • Lists all package authors with emails and ORCIDs where available

• Source of truth alignment

  • Mirrors the canonical author list from DESCRIPTION
  • Uses the current package version to keep citation metadata in sync with the release line

cff-version: 1.2.0
title: "Tables and Figures for Stock Assessments"
version: "0.15.0"
authors:
  - family-names: "Schiano"
    given-names: "Samantha"

[github-actions]

Code Metrics Report

Coverage	Code to Test Ratio	Test Execution Time
71.4%	1:0.2	8m57s

Code coverage of files in pull request scope (54.7%)

Files	Coverage
R/convert_output.R	54.7%

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Reported by octocov