@StyleSheet doesn't work with root level frontend resources

[tomivirkki]

Not sure if this is an issue with documentation, Flow or the starters.

Added @StyleSheet("styles.css") as advised here and it seems to be looking for the file from under "http://localhost:8080/frontend/styles.css" (also the annotation docs mentions the "frontend" folder) which could be assumed to be the root level "frontend" folder.

Vaadin servlet doesn't however share dynamic resources from that folder so you'll need to place the css file under "src/main/webapp/frontend" instead, which doesn't exist by default in the V14 starter projects (it did with V13 starters).

[pleku]

Acceptance Criteria

• [ ] Remove the documentation for @StyleSheet, meaning this file https://github.com/vaadin/flow-and-components-documentation/blob/master/documentation/importing-dependencies/tutorial-include-css.asciidoc, and adjust the page ordering for other files in the chapter
• [ ] Change the name of the theming topic from Theming Flow Applications into Theming Applications with CSS here https://github.com/vaadin/vaadin-docs/blob/d351db968e104e5851c90e2783759402d45105d9/website/_data/docs.yml#L18 for V14 branch
• [ ] Change the name of the importing dependencies topic from Importing HTML, JavaScript and CSS files into Importing JavaScript and HTML here https://github.com/vaadin/vaadin-docs/blob/d351db968e104e5851c90e2783759402d45105d9/website/_data/docs.yml#L16 for V14 branch
• [ ] Make sure there are no mentions to @StyleSheet in the documentation anymore