linter: allow expressions in JSX fragment

[ptamarit]

❤️ Thank you for your contribution!

Description

We get quite a lot of ESLint warnings across inveniosoftware repositories for following the pattern <>{foo}</>.
There are a few places were we explicitly inline-disable the check, and other places were we ignore the warning.

This pull request proposes to relax this ESLint rule to allow this pattern (see the react/jsx-no-useless-fragment documentation).
If you agree with it, I will apply this change to:

• inveniosoftware/eslint-config-invenio (linter: allow expressions in JSX fragment & release: v2.0.2 eslint-config-invenio#16)
• as well as inveniosoftware/demo-invenioils (linter: allow expressions in JSX fragment demo-invenioils#17)
• and inveniosoftware/cookiecutter-invenio-ils (linter: allow expressions in JSX fragment cookiecutter-invenio-ils#3)

Checklist

Ticks in all boxes and 🟢 on all GitHub actions status checks are required to merge:

• I'm aware of the code of conduct.
• I've created logical separate commits and followed the commit message format.
• I've added relevant test cases.
• I've added relevant documentation.
• I've marked translation strings.
• I've identified the copyright holder(s) and updated copyright headers for touched files (>15 lines contributions).
• I've NOT included third-party code (copy/pasted source code or new dependencies).
  • If you have added third-party code (copy/pasted or new dependencies), please reach out to an architect.

Frontend

• I've followed the CSS/JS and React guidelines.
• I've followed the web accessibility guidelines.
• I've followed the user interface guidelines.

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[ptamarit]

After some discussion, we decided that we should fix these useless fragment problems instead of relaxing the ESLint rule.
FYI, an example of how to fix the useless fragment problems can be found here: inveniosoftware/invenio-app-rdm@59bfa2b