Consistent Headline Capitalization?

Is this book using Headline Capitalization or Sentence capitaliztion for headers? From a quick scan it seems Headline Capitalization is used (except when it isn't).

E.g. in Constructors:

Default Constructors vs. See also (should be See Also, this is incorrectly capitalized everywhere I looked).

Or in Struct decomposition for independent borrowing (should be Struct Decomposition for Independent Borrowing).

Etc.

Would you accept a PR that unifies this?