[sld-viewer] npm audit fix vulnerabilities

[flo-dup]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem? No

What kind of change does this PR introduce? Vulnerabilities fix

What is the current behavior? npm install lists 5 vulnerabilities (4 moderate, 1 high)

What is the new behavior (if this is a feature change)? npm install lists no vulnerabilities

Does this PR introduce a breaking change or deprecate an API?

• [ ] Yes
• [x] No

[flo-dup]

Has been fixed in #54