Implement LZSS decompression with optional XOR decryption

- Added `lzss_decompress_simple` function for LZSS decompression in `lzss.rs`.
- Introduced `XorState` struct and `xor_stream` function for XOR decryption in `xor.rs`.
- Updated `mod.rs` to include new LZSS and XOR modules.
- Refactored `parse_library` function in `parse.rs` to utilize the new XOR decryption functionality.
- Cleaned up and organized code in `lib.rs` by removing redundant functions and structures.
- Added tests for new functionality in `tests.rs`.

crates/rsli/src/compress/mod.rs

@@ -0,0 +1,9 @@
+pub mod deflate;
+pub mod lzh;
+pub mod lzss;
+pub mod xor;
+
+pub use deflate::decode_deflate;
+pub use lzh::lzss_huffman_decompress;
+pub use lzss::lzss_decompress_simple;
+pub use xor::{xor_stream, XorState};