Merge pull request #80504 from daveyc123/doccForDiagnostics

Prepare diagnostics docs for docc generation

Author: daveyc123

userdocs/diagnostics/.gitignore

@@ -0,0 +1 @@
+.docc-build

userdocs/diagnostics/async-caller-execution.md

@@ -1,14 +1,15 @@
 # `AsyncCallerExecution`
 
-Proposed in [SE-0461], this feature changes the behavior of nonisolated async
+This feature changes the behavior of nonisolated async
 functions to run on the actor to which the caller is isolated (if any) by 
 default, and provides an explicit way to express the execution semantics for
-these functions:
+these functions.
+
+This feature was proposed in [SE-0461](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0461-async-function-isolation.md)
+
 * The `@execution(concurrent)` attribute specifies that a function must always 
   switch off of an actor to run.
   This is the default behavior without `AsyncCallerExecution`.
 * The `@execution(caller)` attribute specifies that a function must always 
   run on the caller's actor.
   This is the default behavior with `AsyncCallerExecution`.
-
-[SE-0461]: https://github.com/swiftlang/swift-evolution/blob/main/proposals/0461-async-function-isolation.md

userdocs/diagnostics/diagnostics.md

@@ -0,0 +1,7 @@
+# Swift Compiler Diagnostics
+
+@Metadata {
+   @TechnologyRoot
+}
+
+Documentation on diagnostics emitted by the compiler.

userdocs/diagnostics/existential-any.md

@@ -1,7 +1,9 @@
 # `ExistentialAny`
 
 This diagnostic group includes errors and warnings pertaining to the `any` type
-syntax proposed in [SE-0335].
+syntax.
+
+This syntax was proposed in [SE-0335](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0335-existential-any.md).
 `any` syntax draws a line between constraint types and existential or boxed
 types.
 
@@ -20,5 +22,3 @@ func sillyFunction(collection: Collection) { // error
   // ...
 }
 ```
-
-[SE-0335]: https://github.com/swiftlang/swift-evolution/blob/main/proposals/0335-existential-any.md