docs: add comprehensive user guide and getting started documentation

[thkruz]

• Add extensive user guide covering all OOTK features

  • Satellite operations and tracking
  • Sensor operations and pass predictions
  • Coordinate systems and transformations
  • Orbit propagation methods
  • Force models and perturbations
  • Initial orbit determination
  • Observations and time systems
  • Interpolation and mathematical operations
  • Optimization and covariance
  • Celestial bodies and maneuvers
  • Advanced topics and performance tips

• Add getting started guide for new users

  • Step-by-step installation instructions
  • Tutorial for tracking first satellite
  • Explanation of coordinate systems
  • Working with sensors and pass predictions
  • Common use cases with complete examples
  • Troubleshooting section
  • Quick reference and example projects

• Add documentation index (docs/README.md)

  • Navigation guide for all documentation
  • Quick links to key topics
  • Clear structure for beginners vs advanced users

• Update main README.md with documentation links

[github-actions]

# npm audit report

brace-expansion  1.0.0 - 1.1.11
brace-expansion Regular Expression Denial of Service vulnerability - https://github.com/advisories/GHSA-v6h2-p8h4-qcjw
fix available via `npm audit fix`
node_modules/brace-expansion

js-yaml  <3.14.2 || >=4.0.0 <4.1.1
Severity: moderate
js-yaml has prototype pollution in merge (<<) - https://github.com/advisories/GHSA-mh29-5h37-fv8m
js-yaml has prototype pollution in merge (<<) - https://github.com/advisories/GHSA-mh29-5h37-fv8m
fix available via `npm audit fix`
node_modules/@eslint/eslintrc/node_modules/js-yaml
node_modules/eslint/node_modules/js-yaml
node_modules/js-yaml

2 vulnerabilities (1 low, 1 moderate)

To address all issues, run:
  npm audit fix