Add visionOS extension to platform lists.

Confirmed this is supported as of swiftlang-5.9.2.2.56.

Author: amartini51

TSPL.docc/ReferenceManual/Attributes.md

@@ -154,6 +154,7 @@ These arguments begin with one of the following platform or language names:
 - `tvOS`
 - `tvOSApplicationExtension`
 - `visionOS`
+- `visionOSApplicationExtension`
 - `swift`
 
 <!--

TSPL.docc/ReferenceManual/Statements.md

@@ -1337,7 +1337,7 @@ It has the same meaning as the `*` argument in an availability condition.
 > *platform-name* → **`macCatalyst`** | **`macCatalystApplicationExtension`** \
 > *platform-name* → **`watchOS`** | **`watchOSApplicationExtension`** \
 > *platform-name* → **`tvOS`** | **`tvOSApplicationExtension`** \
-> *platform-name* → **`visionOS`** \
+> *platform-name* → **`visionOS`** | **`visionOSApplicationExtension`** \
 > *platform-version* → *decimal-digits* \
 > *platform-version* → *decimal-digits* **`.`** *decimal-digits* \
 > *platform-version* → *decimal-digits* **`.`** *decimal-digits* **`.`** *decimal-digits*

TSPL.docc/ReferenceManual/SummaryOfTheGrammar.md

@@ -723,7 +723,7 @@ make the same change here also.
 > *platform-name* → **`macCatalyst`** | **`macCatalystApplicationExtension`** \
 > *platform-name* → **`watchOS`** | **`watchOSApplicationExtension`** \
 > *platform-name* → **`tvOS`** | **`tvOSApplicationExtension`** \
-> *platform-name* → **`visionOS`** \
+> *platform-name* → **`visionOS`** | **`visionOSApplicationExtension`** \
 > *platform-version* → *decimal-digits* \
 > *platform-version* → *decimal-digits* **`.`** *decimal-digits* \
 > *platform-version* → *decimal-digits* **`.`** *decimal-digits* **`.`** *decimal-digits*