Prepare for the 2.11 dev SDKs (#55)

Bump the upper bound to allow 2.10 stable and 2.11.0 dev SDK versions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5af5752..fe19761 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.10.10-nullsafety.1
+
+* Allow 2.10 stable and 2.11.0 dev SDK versions.
+
 ## 0.10.10-nullsafety
 
 * Migrate to null safety
diff --git a/pubspec.yaml b/pubspec.yaml
index 1951d72..a61224a 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,12 +1,12 @@
 name: source_maps
-version: 0.10.10-nullsafety
+version: 0.10.10-nullsafety.1
 
 description: Library to programmatically manipulate source map files.
 homepage: https://github.com/dart-lang/source_maps
 
 environment:
   # This must remain a tight constraint until nnbd is stable
-  sdk: '>=2.10.0-0 <2.10.0'
+  sdk: '>=2.10.0-0 <2.11.0'
 
 dependencies:
   source_span: '>=1.8.0-nullsafety <1.8.0'