docs: documented the heap

.wiki/Kernel-documentation.md

@@ -240,6 +240,37 @@ More information can be found on the limine project's [GitHub](https://github.co
 
 ## mm
 
+### heap.h
+
+#### `heap_segment_T` - struct
+This is the header for each heap segment.
+It holds its status information and a pointer to the next and previous segments.
+It lies in memory, directly before the accessible buffer of the segment.
+
+#### `heap_T` - struct
+This struct describes a heap.
+The area between **_start_** and **_end_** is filled with heap segments.
+
+#### `heap_create(base)` - function (void)
+Creates a heap starting at **_base_** (virtual address).
+It will automatically map some page frames to that address.
+
+#### `heap_memory_allocate(heap*, size)` - function (void)
+Returns a pointer to a free usable memory location, that has at least the given **_size_**.
+It will return `NULL` and log an error, if the heap is corrupted.
+Because this function iterates over the complete heap to find a free segment, it is slow.
+
+#### `heap_memory_free(heap*, address)` - function (void)
+Frees a with `heap_memory_allocate` created heap segment, and makes it usable again.
+Does nothing, if the address doesn't point to a valid heap segment.
+
+#### `heap_dump_segments(heap*)` - function (void)
+Logs a complete list, of all heap segments.
+Useful, when debugging / testing the heap.
+
+#### `heap_destruct(heap*)` - function (void)
+Invalidates all segments of a heap, frees all used page frames and unmaps them.
+
 ### memory_map.h
 
 #### `memory_map_get_total_memory_size(boot_info*)` - function (uint64_t)