Add Docker and GitHub Actions CI for PHP 8.2-8.5 on Debian and Alpine

Separate Dockerfiles for Debian and Alpine with parameterized PHP
version. CI matrix tests 8 combinations (4 PHP versions x 2 platforms).
Added .dockerignore to prevent stale host build artifacts from
corrupting cross-version Docker builds.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Bump version to 2.0.1 (2.0.0 already exists on PECL as alpha)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Rename toSci to toScientific, add missing tests, update package.xml

- Rename toSci method to toScientific on Decimal, Rational, and Number
- Add tests for Decimal::isPositive, Decimal::isNegative
- Add tests for Rational::isPositive, Rational::isNegative
- Add test for Rational::trunc
- Add test for Rational::toScientific
- Update package.xml with all test files and release notes
- Update CHANGELOG.md for v2.0.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

v1.5.3 - Fix get_properties_for for PHP 7.4, set min PHP 7.4

v1.5.2 - Add composer.json for PIE/Packagist support

v1.5.1 - Fix isPositive/isNegative for zero, add array cast support, …

…PIE support

Local development script, v1.5.0

Local development script, v1.5.0

Update changelog to include 1.4.0

Update package changelog