v1.4.2: Update documentation

What's Changed

• Add issue templates by @Aeliot-Tm in #43
• Add authors into composer.json by @Aeliot-Tm in #44
• Update keywords in composer.json by @Aeliot-Tm in #47
• Add license header into php-files by @Aeliot-Tm in #46
• Add SECURITY.md by @Aeliot-Tm in #45

Full Changelog: v1.4.1...v1.4.2