Clairify versioning gaurentees

Author: aDotInTheVoid

text/0000-rustdoc-types-maintainers.md

@@ -55,8 +55,10 @@ The update/publishing process will be moved to T-Rustdoc. In the medium term, I
 - In an official capacity
 - With bus factor for when I stop.
 
-We will continue to publish new version of the `rustdoc-types` crate every time
-the upstream implementation changes.
+We (T-Rustdoc) will continue to publish new version of the `rustdoc-types` crate
+every time the upstream implementation changes, and these will be versioned with
+normal semver. Changes to rustdoc-json in `rust-lang/rust` will not be accepted
+if they would make it not possible to publish `rustdoc-types`.
 
 ## Actual Mechanics of the move