merge package from arlac77/npm-package-template-esm-only

[arlac77]

package.json

• chore(package): esm@^3.2.18
• chore(scripts): cover@#overwrite c8 --temp-directory build/coverage ava && c8 report -r lcov --temp-directory build/coverage
• chore(scripts): posttest@markdown-doctest
• docs(package): remove keyword null

.travis.yml

• chore(travis): remove node versions 11.11.0
• chore(travis): add node versions -10,-11,11.12.0

[arlac77]

:tada: This PR is included in version 5.0.1 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: