test: compile web3.js tests in such a way that you can use es2020+ syntax without crashing Mocha

Author: steveluscher

package.json

@@ -50,7 +50,7 @@
     "pretty": "prettier --check '{,{src,test}/**/}*.{j,t}s'",
     "pretty:fix": "prettier --write '{,{src,test}/**/}*.{j,t}s'",
     "re": "semantic-release --repository-url git@github.com:solana-labs/solana-web3.js.git",
-    "test": "cross-env TS_NODE_COMPILER_OPTIONS='{ \"module\": \"commonjs\" }' ts-mocha --require esm './test/**/*.test.ts'",
+    "test": "cross-env TS_NODE_COMPILER_OPTIONS='{ \"module\": \"commonjs\", \"target\": \"es2019\" }' ts-mocha --require esm './test/**/*.test.ts'",
     "test:cover": "nyc --reporter=lcov npm run test",
     "test:live": "TEST_LIVE=1 npm run test",
     "test:live-with-test-validator": "start-server-and-test 'solana-test-validator --reset --quiet' http://localhost:8899/health test:live"