Improve definitions at composer.json

[phansys]

• Update version constraints in order to respect SemVer;
• Add missing requirement for "ext-curl" and "ext-json";
• Fix "type" value according schema;
• Suggest "ext-fileinfo", since it's useful at APIRequest::uploadFile();
• Add "extra.branch-alias" definition in order to allow dev installs using SemVer;
• Add "config.sort-packages" definition;
• Add "keywords" definition in order to list the keywords related to the library.