Fix misspellings

src/inc/til/rle.h

@@ -929,7 +929,7 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
             {
                 mid_insertion_trailer.emplace(begin->value, static_cast<size_type>(begin->length - end_pos));
                 // mid_insertion_trailer contains the element that will be inserted past
-                // the to-be-replaced range. We must ensure that we don't accidentially
+                // the to-be-replaced range. We must ensure that we don't accidentally
                 // adjust the length of an unrelated run and thus set end_post to 0.
                 end_pos = 0;
             }