IDS-9779: Fix modeler elements error

[voxparcxls]

• This error is encountered when running the install modeler script outside of /modeler without elements.json

cp: ../elements.json: No such file or directory

• This commit adds a warning to the user to run the script from inside /modeler OR have elements.json in the same directory as the modeler script.

If elements.json file is not in the same directory as install_mac_modeler.sh script, it gives a warning.

(base) MT-304569:modeler haile$ ./install_mac_modeler.sh 

Camunda Modeler Installer for Mac OS

****************************************
*************** WARNING ! **************
****************************************
+--------------------------------------+
File 'elements.json' does not exists in /Users/haile/dev_cws/common-workflow-service/install/modeler directory   
+--------------------------------------+

Run the Camunda Modeler Installer from 'modeler/' folder or copy elements.json to /Users/haile/dev_cws/common-workflow-service/install/modeler before continuing 

Installing in '/Applications' directory

*** Warning! ***  This will remove your old Camunda Modeler (if exists) and install the latest version...

Press Y to continue or N to abort. (Y/N):