Make 10 the default value for ecmaVersion

Author: marijnh

acorn/README.md

@@ -54,7 +54,7 @@ an object containing any of these fields:
 - **ecmaVersion**: Indicates the ECMAScript version to parse. Must be
   either 3, 5, 6 (2015), 7 (2016), 8 (2017), 9 (2018) or 10 (2019, partial
   support). This influences support for strict mode, the set of
-  reserved words, and support for new syntax features. Default is 9.
+  reserved words, and support for new syntax features. Default is 10.
 
   **NOTE**: Only 'stage 4' (finalized) ECMAScript features are being
   implemented by Acorn. Other proposed new features can be implemented

acorn/src/options.js

@@ -9,8 +9,8 @@ export const defaultOptions = {
   // either 3, 5, 6 (2015), 7 (2016), 8 (2017), 9 (2018), or 10
   // (2019). This influences support for strict mode, the set of
   // reserved words, and support for new syntax features. The default
-  // is 9.
-  ecmaVersion: 9,
+  // is 10.
+  ecmaVersion: 10,
   // `sourceType` indicates the mode the code should be parsed in.
   // Can be either `"script"` or `"module"`. This influences global
   // strict mode and parsing of `import` and `export` declarations.