Add ability to write DICOM files from NIfTI without a reference

[sarthakpati]

Is your feature request related to a problem? Please describe.
Currently, DICOM images can only be written from a NIfTI if a reference DICOM is present, which is not always the case.

Describe the solution you'd like
Add the ability to write DICOM files from NIfTI without a reference image.

Describe alternatives you've considered
N.A.

Additional context

• Ensure DICOM validity 🙄.
• Requested by @sbakas

[sarthakpati]

Tracking in https://github.com/sarthakpati/CaPTk/tree/dicom