feat(issue-155): Allow multiple file upload

[tallulahh]

Issue #, if available: 155 - #155

Description of changes: Allow multiple file selection and upload.
While working on a project we required this feature, this code enabled us to select multiple files and upload them.

What was done:

• updated b-form-file element to use multiple
• updated data to return an array for fileToUpload
• updated the uploadChunk method to accept the file as a parameter and pass parameter into function. Updated all instances of this method being called.
• updated the checkIfFileExists method to loop through the fileToUpload array. If no files already exist, it will loop through the files, calling the upload method on each file. When the for loop finished it will call the afterComplete method to output a successful message.
• updated the upload method to accept the file parameter and pass parameter into function. Updated all instances of this method being called. Commented all calls of afterComplete from within this function, as it is being called after the loop of uploading files is complete.

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