more typos h/t Arnaud

NEWS.md

@@ -9,7 +9,7 @@
 
   - We added an argument for LIFO cleanup: `on.exit(after = FALSE)`.
   - Calling `sys.on.exit()` elsewhere than top-level didn't work. This
-    is needed for manual invokation with `deferred_run()`.
+    is needed for manual invocation with `deferred_run()`.
 
   Following this change, `defer()` is now much faster (although still
   slower than `on.exit()` which is a primitive function and about as
@@ -25,7 +25,7 @@
   `globalenv()` (the default), you now need to set
   `options(withr.hook_source = TRUE)` to get proper withr support
   (running `defer()` or `local_` functions at top-level of a script).
-  THis support is disabled by default in local environments to avoid a
+  This support is disabled by default in local environments to avoid a
   performance penalty in normal usage of withr features.