Add `simd.indices` and docs

base/intrinsics/intrinsics.odin

@@ -298,7 +298,7 @@ simd_masked_store :: proc(ptr: rawptr, val: #simd[N]T, mask: #simd[N]U)
 simd_masked_expand_load    :: proc(ptr: rawptr, val: #simd[N]T, mask: #simd[N]U) -> #simd[N]T where type_is_integer(U) || type_is_boolean(U) ---
 simd_masked_compress_store :: proc(ptr: rawptr, val: #simd[N]T, mask: #simd[N]U)              where type_is_integer(U) || type_is_boolean(U) ---
 
-
+simd_indices :: proc($T: typeid/#simd[$N]$E) -> T where type_is_numeric(T) ---
 
 simd_shuffle :: proc(a, b: #simd[N]T, indices: ..int) -> #simd[len(indices)]T ---
 simd_select  :: proc(cond: #simd[N]boolean_or_integer, true, false: #simd[N]T) -> #simd[N]T ---

core/simd/simd.odin

@@ -2510,3 +2510,17 @@ Example:
 recip :: #force_inline proc "contextless" (v: $T/#simd[$LANES]$E) -> T where intrinsics.type_is_float(E) {
 	return T(1) / v
 }
+
+
+/*
+Create a vector where each lane contains the index of that lane.
+Inputs:
+- `V`: The type of the vector to create.
+Result:
+- A vector of the given type, where each lane contains the index of that lane.
+**Operation**:
+	for i in 0 ..< N {
+		res[i] = i
+	}
+*/
+indices :: intrinsics.simd_indices