Release 0.2.0

Add support for more libraries and standard types

• Add optional support for many more external libraries: slotmap, slab, indexmap, arrayvec, smallvec, hashbrown, and chrono
• Add support for many more standard library types
• No longer count references into the total size; they are not owned data (This does not apply to reference counted data)
• Fix potential UB and remove unsafe usage for tracking visited references
• Update HashMap size estimation for hashbrown usage in std