[ox/std] Add BasicString<0> instantiation

(synced from a9b5bfe438)

src/ox/std/string.cpp

@@ -9,4 +9,7 @@
 #include "string.hpp"
 
 namespace ox {
+
+template class BasicString<0>;
+
 }

src/ox/std/string.hpp

@@ -399,6 +399,8 @@ constexpr std::size_t BasicString<SmallStringSize>::len() const noexcept {
 	return length;
 }
 
+extern template class BasicString<0>;
+
 using String = BasicString<0>;
 
 }