Small vue-cli-3 fix allowing the backend pom file to copy the frontend static resources on project compilation

[angelomelonas]

I noticed that after compiling (mvn clean install), running the project (--projects backend spring-boot:run) and visiting http://localhost:8088 that a blank page was shown (even though running the frontend in a dev environment it works perfectly). It turns out that the backend pom file, which is instructed to copy assets from the frontend/target/dist and frontend/target/dist/static folders to the backend resources folder, only copies the index.html file and not the static assets.
After the recent vue-cli-3 upgrade the static assets are no longer placed in the frontend/target/dist/static folder, thus adding assetsDir: 'static' to the vue.config.js file ensures the backend can copy the static assets upon compilation.

[coveralls]

Pull Request Test Coverage Report for Build 97

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.103%

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Totals
Change from base Build 96:	0.0%
Covered Lines:	27
Relevant Lines:	29

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💛 - Coveralls

[jonashackt]

Hey @angelomelonas , you´re absolutely right 👍 This line was left and also meant, that the Heroku deployment was broken. Thank you very much.