Add Armstrong_Number.rs

[ajayjha5899]

Fixes #2120

Checklist:

• [x] 4 space indentation.
• [x] Coding conventions are followed.
• [x] Input is taken dynamically.
• [x] Sample Input / Output is added at the end of file.
• [x] Logic Documentation (Comments).
• [x] File names are correct.

Make sure these boxes are checked before your pull request (PR) is ready to be reviewed and merged. Thanks!

Changes proposed in this pull request:

• Added Armstrong_Numbers.rs file.
• It is a program in Rust which determines whether a number is Armstrong number or not. The number is taken as input from the user.

Languages Used:

• Rust

Files Added:

• ./Algo_Ds_Notes/Armstrong_Number/Armstrong_Numbers.rs

Thanks!