Add Development Notes

Development-Notes.md

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+## Lua's error handling breaks Rust's memory safety
+
+Since Lua utilizes `longjmp` for error handling and stack unwinding, any Lua error that crosses a Rust stack frame is going to lead to memory leaks from skipping `drop`s and to borrow checker constraints being broken.
+
+The problem is that many Lua functions create errors internally. Some of them cannot be avoided (e.g. OOM), but wherever possible, per-conditions need to be checked such that Lua does not `longjmp`.
+E.g. a `lua.tostring` must be preceded by a `lua.isstring`.