Spec: Add 'see also' sections to pages which don't have it

Author: rail5

wiki/spec/interoperability.md

@@ -31,3 +31,8 @@ The behavior of `set` is therefore undefined in Bash++ programs.
 # NOTES
 
 These features are not banned and you are free to use them as you see fit. However, their behavior is **undefined** as far as Bash++ is concerned. This means that the Bash++ compiler will not enforce any rules regarding their use, and the behavior of your program may vary depending on how you use them.
+
+# SEE ALSO
+
+ - [bpp-string-interpolation(3)](string-interpolation.md) for more information on string interpolation in Bash++
+ - [bpp-value-categories(3)](value-categories.md) for more information on lvalues and rvalues in Bash++, and how these value categories differ from those in Bash

wiki/spec/typeof.md

@@ -44,3 +44,7 @@ The `@typeof` directive expands to the result described above. This result is th
 The *input* to the `@typeof` directive is that which is being inspected. The input can be any rvalue at all, but *should* be a pointer to an object.
 
 An easy mistake to make, for example, would be to pass an object directly instead of its address -- this would implicitly call the object's `toPrimitive` method, and attempt to find the "type of" that method's output.
+
+# SEE ALSO
+
+ - [bpp-classes(3)](classes.md) for more information on classes

wiki/spec/value-categories.md

@@ -146,3 +146,8 @@ In the above case, we consider `$var` to be an lvalue, because it is the first n
 However, because it expands to the empty string, the "command word" is actually `echo`, and the above code will output "hi" rather than producing an error about an invalid command.
 
 The compiler, however, cannot predict how variables will expand at runtime (this is computationally undecidable). The categorization of symbols into "lvalues" and "rvalues" therefore is based solely on source position, and only incidentally corresponds (in the vast majority of cases) to whether that symbol can be executed as a command.
+
+# SEE ALSO
+
+ - [bpp-methods(3)](methods.md) for more information on object methods
+ - [bpp-supershell(3)](supershell.md) for more information on supershells