Remove functions

In this MR we:

• Updated the installing instructions in the README file because the npm module Java cannot be installed with JDK 17 in Mac.
• Removed the function setExtensionElementValue that was duplicated in files bpmnSetcstnuLabels.js and cstnuChecked.js and used instead of the one in wondow.bpmnjs.
• In the script bpmn2cstnu.js the values minDuration and maxDuration are checked for the elements, sequenceFlow, and relativeConstraints. There were three functions that performed this checking, but they had a big common section. This section was removed from those functions and moved in a common function used for the others, to do not have duplicated sections of the code.
• Added the file package-lock.json with the package versions compatibles with the application.
• Improved comments