Patch release 1.0.4 of the SPDX Java V3 JSON-LD Store

What's Changed

• Update JsonNode.properties() instead of .fields() by @bact in #83
• Add javadoc to JsonLDSchema class by @bact in #84
• Add Maven Central badge by @bact in #81
• More Yocto SPDX parsing fixes by @sschuberth in #82

Full Changelog: v1.0.3...v1.0.4