AK: Add epsilon() to NumericLimits for float, double, long double

Author: https://github.com/sunverwerth
Commit: https://github.com/SerenityOS/serenity/commit/0a557d65a0b
Pull-request: https://github.com/SerenityOS/serenity/pull/6375
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/IdanHo
Reviewed-by: https://github.com/Quaker762
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/ccapitalK
Reviewed-by: https://github.com/gmta

AK/NumericLimits.h

@@ -103,6 +103,7 @@ template<>
 struct NumericLimits<float> {
     static constexpr float min() { return __FLT_MIN__; }
     static constexpr float max() { return __FLT_MAX__; }
+    static constexpr float epsilon() { return __FLT_EPSILON__; }
     static constexpr bool is_signed() { return true; }
 };
 
@@ -110,6 +111,7 @@ template<>
 struct NumericLimits<double> {
     static constexpr double min() { return __DBL_MIN__; }
     static constexpr double max() { return __DBL_MAX__; }
+    static constexpr double epsilon() { return __DBL_EPSILON__; }
     static constexpr bool is_signed() { return true; }
 };
 
@@ -117,6 +119,7 @@ template<>
 struct NumericLimits<long double> {
     static constexpr long double min() { return __LDBL_MIN__; }
     static constexpr long double max() { return __LDBL_MAX__; }
+    static constexpr long double epsilon() { return __LDBL_EPSILON__; }
     static constexpr bool is_signed() { return true; }
 };
 #endif