Security upgrade node from lts-buster to current-slim

[cloudgeek7]

Keeping your Docker base image up-to-date means you’ll benefit from security fixes in the latest version of your chosen image.

Changes included in this PR

• react-express-mongodb/frontend/Dockerfile

We recommend upgrading to node:current-slim, as this image has only 44 known vulnerabilities. To do this, merge this pull request, then verify your application still works as expected.

Some of the most important vulnerabilities in your base image include:

Severity	Priority Score / 1000	Issue	Exploit Maturity
Critical	500	Integer Overflow or WraparoundSNYK-DEBIAN10-EXPAT-2331803	No Known Exploit
Critical	500	Integer Overflow or WraparoundSNYK-DEBIAN10-EXPAT-2331813	No Known Exploit
Critical	500	Integer Overflow or WraparoundSNYK-DEBIAN10-EXPAT-2331818	No Known Exploit
Critical	500	Integer Overflow or WraparoundSNYK-DEBIAN10-EXPAT-2359258	No Known Exploit
Critical	500	Integer Overflow or WraparoundSNYK-DEBIAN10-EXPAT-2384929	No Known Exploit