chore: update npm on travis

Author: achingbrain

.travis.yml

@@ -24,6 +24,8 @@ os:
 before_install:
   # prevents windows error: npm ERR! ... git-sh-setup: file not found
   - if [ "$TRAVIS_OS_NAME" = "windows" ]; then export PATH=/c/PROGRA~1/Git/usr/bin:/c/PROGRA~1/Git/mingw64/libexec/git-core:$PATH ; fi
+  # workspaces requires npm >= 7
+  - npm install -g npm@>=7
 
 script: npx nyc -s npm run test:node -- --bail
 after_success: npx nyc report --reporter=text-lcov > coverage.lcov && npx codecov