Docs: Fix typos in interface package (#29740)

* Docs: Fix typo

* Docs: Reword

* Docs: Fix typo

packages/interface/README.md

@@ -1,6 +1,6 @@
 # (Experimental) Interface
 
-The Interface Package contains the basis the start a new WordPress screen as Edit Post or Edit Site. The package offers a data store and a set of components. The store is useful to contain common data required by a screen (e.g., active areas). The information is persisted across screen reloads. The components allow one to implement functionality like a sidebar or menu items. Third-party plugins by default, can extend them.
+The Interface Package contains the basis to start a new WordPress screen as Edit Post or Edit Site. The package offers a data store and a set of components. The store is useful to contain common data required by a screen (e.g., active areas). The information is persisted across screen reloads. The components allow one to implement functionality like a sidebar or menu items. Third-party plugins can extend them by default.
 
 ## Installation
 
@@ -17,7 +17,7 @@ _This package assumes that your code will run in an **ES2015+** environment. If
 
 ### Complementary Areas
 
-This component was named after a [complementatry landmark](https://www.w3.org/TR/wai-aria-practices/examples/landmarks/complementary.html) – a supporting section of the document, designed to be complementary to the main content at a similar level in the DOM hierarchy, but remains meaningful when separated from the main content.
+This component was named after a [complementary landmark](https://www.w3.org/TR/wai-aria-practices/examples/landmarks/complementary.html) – a supporting section of the document, designed to be complementary to the main content at a similar level in the DOM hierarchy, but remains meaningful when separated from the main content.
 
 `ComplementaryArea` and `ComplementaryArea.Slot` form a slot fill pair to render complementary areas. Multiple `ComplementaryArea` components representing different complementary areas may be rendered at the same time, but only one appears on the slot depending on which complementary area is enabled.