Create Sum_of_digits_recursion.c

[Aditi22Bansal]

Description:

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #issue_number_here
#415

Type of change:

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.
• Necessary documentation changes done
• I have added the file in the correct directory

Screenshots / Video:

[Aditi22Bansal]

@Kavya-24
Kindly review and merge
If any changes are required kindly tell
Thankyou