Исправление и расширение документации по векторам и кватернионам

docs/quaternion/reset-eng.md

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+# Resetting the state of a Quaternion
+
+[Русская версия / Russian version](reset-rus.md)
+
+These functions set all parts of a quaternion to 0.
+
+Function for **BGC_FP32_Quaternion**:
+
+```c
+inline void bgc_fp32_quaternion_reset(BGC_FP32_Quaternion* const quaternion);
+```
+
+Function for **BGC_FP64_Quaternion**:
+
+```c
+inline void bgc_fp64_quaternion_reset(BGC_FP64_Quaternion* const quaternion);
+```
+
+Each of these functions is equivalent to the following lines of code:
+
+```c
+vector->x = 0;
+vector->y = 0;
+```
+
+You should pass valid pointers to these functions. The NULL (0) value is also
+considered invalid.
+
+This function is good for setting up the initial state of a quaternion.
+
+Example of use:
+
+```c
+#include <stdio.h>
+#include <basic-geometry.h>
+
+int main()
+{
+    BGC_FP64_Quaternion quaternion;
+
+    bgc_fp32_quaternion_reset(&quaternion);
+
+    printf("s = %lf, x = %lf, y = %lf, z = %lf\n", quaternion.s, quaternion.x, quaternion.y, quaternion.z);
+
+    return 0;
+}
+```
+
+[Documentation](../intro-eng.md) / [2D vectors](../quaternion-eng.md)