Add README for Day 02 medium level programs

Added a README file outlining the medium-level number programming problems and objectives.

Author: curious-vasavi

src/number_Programming/medium/day_02/README.md

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+## Medium Level Number Programming – Day 02
+
+This folder contains medium-level Java number programming problems focused on
+digit manipulation, prime logic, factors, and mathematical reasoning.
+
+### Topics Covered
+- Multiplication table of a number
+- Prime number check
+- Sum and product of prime numbers in a range
+- Factors of a number (sum & product)
+- Even and odd factors
+- Digit-based operations:
+  - Count of digits
+  - Even digits
+  - Odd digits
+  - Sum & product of digits
+  - Prime digits
+  - Factorial of digits
+
+### Objective
+- Strengthen loop-based logic
+- Improve number and digit manipulation skills
+- Practice conditional checks and modular arithmetic
+- Write clean Java methods using Scanner input
+
+Each problem is implemented as a **separate Java file** for clarity and practice.