Add Radian converter to main README.

Author: trekhleb

README.md

@@ -70,6 +70,7 @@ a set of rules that precisely define a sequence of operations.
   * `B` [Is Power of Two](src/algorithms/math/is-power-of-two) - check if the number is power of two (naive and bitwise algorithms)
   * `B` [Pascal's Triangle](src/algorithms/math/pascal-triangle)
   * `B` [Complex Number](src/algorithms/math/complex-number) - complex numbers and basic operations with them
+  * `B` [Radian & Degree](src/algorithms/math/radian) - radians to degree and backwards conversion
   * `A` [Integer Partition](src/algorithms/math/integer-partition)
   * `A` [Liu Hui π Algorithm](src/algorithms/math/liu-hui) - approximate π calculations based on N-gons
 * **Sets**