Changelog updates (#114)

Changelog.md

@@ -10,6 +10,29 @@
 
 * `EitherTable`, `ListTable`, `MaybeTable`, `NonEmptyTable` and `TheseTable` now all have an extra parameter which tracks the context of the table. If you manually specified any types before, you need to provide this parameter - usually `Expr` will be the correct choice. ([#101](https://github.com/circuithub/rel8/pull/101))
 
+* We've done a lot of work to simplify the internals of Rel8, but some of these are breaking changes. However, most of these API changes shouldn't affect users as they are mostly types used in type inference, or affect classes where users don't need to define their own instances.
+
+  * The kind of a `Rel8able` is now `(Type -> Type) -> Type`. Previously it was `(X -> Type) -> Type`.
+  * `Table` has a new associated type - `FromExprs`. This was previously an open type family.
+  * `Table` has a new associated type - `Transpose` - and `Recontextualise` has been renamed to `Transposes`. This `Transposes` class now operates in terms of `Transpose`.
+
+## New features
+
+* You can derive `Rel8able` for "vanilla" higher-kinded data types - data types that don't use the `Column` type family. For example, the following is now possible:
+
+  ```haskell
+  data MyTable f = MyTable
+    { myTableX :: f Int32
+    , myTableY :: f Text
+    } deriving (Generic, Rel8able)
+  ```
+
+* The `Projectable` and `Biprojectable` type classes have been introduced. These classes model a type of functors and bifunctors (respectively) on tables, where the mapping function is only able to rearrange columns. For example, the following is now possible:
+
+  ```haskell
+  x <- project myTableX <$> many ...
+  ```
+
 ## Bug fixes
 
 * Fixes a bug where cartesian products of queries using `catListTable`, `catNonEmptyTable`, `catList` and `catNonEmpty` would incorrectly be zipped instead. ([#61](https://github.com/circuithub/rel8/pull/61))