Add timer interrupt + PWM work

Readmore.md

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+# Timer Interrupt (ATmega328P)
+
+## Goal
+Generated 1ms interrupt using Timer1
+
+## Key Registers
+- TCCR1B → mode + prescaler
+- OCR1A → compare value
+- TIMSK1 → enable interrupt
+
+## Logic
+Timer counts → match OCR1A → ISR runs → ms++
+
+## Result
+LED blink using ms counter (non-blocking)