chore: add .env.template and update .gitignore for testing infrastructure

Author: lesya7

.env.template

@@ -0,0 +1,19 @@
+# JWT private key 
+TESTKIT_JWT_KEY="-----BEGIN RSA PRIVATE KEY-----
+FAKEPRIVATEKEY1234567890abcdefg==
+-----END RSA PRIVATE KEY-----"
+
+# Connected App Client ID for JWT auth
+TESTKIT_JWT_CLIENT_ID=FAKE_CLIENT_ID_123456
+
+# Username of your Dev Hub org
+TESTKIT_HUB_USERNAME=test-user@example.com
+
+# Path to the Salesforce CLI executable
+TESTKIT_EXECUTABLE_PATH=./node_modules/.bin/sf
+
+# Instance URL of your Dev Hub org
+TESTKIT_HUB_INSTANCE=https://fake-devhub-instance.salesforce.com
+
+# Prevent the dev server from opening the browser during tests
+OPEN_BROWSER=false

.gitignore

@@ -56,4 +56,9 @@ bld
 
 # sf cli
 .sf
-.sfdx
+.sfdx
+
+stdout*
+stderr*
+
+.env