build: updates to pubspec.yaml

- updated `asn1lib` dependency to ^1.5.0
- updated dev dependencies `lints` and `test` to latest versions
- updated sdk from `'>=2.14.0 <3.0.0'` to `'>=2.14.0 <4.0.0'`

Author: gkc

pubspec.yaml

@@ -6,12 +6,12 @@ repository: https://github.com/konstantinullrich/crypton
 issue_tracker: https://github.com/konstantinullrich/crypton/issues
 
 environment:
-  sdk: '>=2.14.0 <3.0.0'
+  sdk: '>=2.14.0 <4.0.0'
 
 dependencies:
   pointycastle: ^3.6.2
-  asn1lib: ^1.2.2
+  asn1lib: ^1.5.0
 
 dev_dependencies:
-  lints: ^1.0.1
-  test: ^1.21.4
+  lints: ^2.1.1
+  test: ^1.24.4