docs: fix stylesheet paths (#4824)

Author: sissbruecker

articles/styling/advanced/reusable-theme.adoc

@@ -36,7 +36,7 @@ acme-theme
 ├── ...
 ----
 
-.src/resources/META-INF/resources/acme-theme/styles.css
+.src/main/resources/META-INF/resources/acme-theme/styles.css
 [source,css]
 ----
 @import 'components.css';
@@ -46,7 +46,7 @@ acme-theme
 
 If the reusable theme should use the Aura or Lumo theme as its foundation, add an `@import` rule to the desired Vaadin theme at the beginning of the reusable theme’s master stylesheet.
 
-.src/resources/META-INF/resources/acme-theme/styles.css
+.src/main/resources/META-INF/resources/acme-theme/styles.css
 [source,css]
 ----
 /* To load the Aura theme */

articles/styling/index.adoc

@@ -33,7 +33,7 @@ public class Application implements AppShellConfigurator {
 
 You can split your CSS over multiple stylesheets, and load them either with separate [annotationname]`@StyleSheet` annotations, or load additional stylesheets using the CSS `@import` rule.
 
-.src/resources/META-INF/resources/styles.css
+.src/main/resources/META-INF/resources/styles.css
 [source,css]
 ----
 @import "additional-styles.css";

articles/styling/stylesheets.adoc

@@ -23,7 +23,7 @@ public class Application implements AppShellConfigurator {
 
 You can split your CSS over multiple stylesheets, and load them either with separate [annotationname]`@StyleSheet` annotations, or load additional stylesheets using the CSS `@import` rule.
 
-.src/resources/META-INF/resources/styles.css
+.src/main/resources/META-INF/resources/styles.css
 [source,css]
 ----
 @import "additional-styles.css";
@@ -46,7 +46,7 @@ public class Application implements AppShellConfigurator {
 }
 ----
 
-.src/resources/META-INF/resources/styles.css
+.src/main/resources/META-INF/resources/styles.css
 [source,css]
 ----
 @import "https://example.com/external-styles.css";
@@ -79,7 +79,7 @@ public class CalendarView extends VerticalLayout {
 }
 ----
 
-.src/resources/META-INF/resources/calendar-view.css
+.src/main/resources/META-INF/resources/calendar-view.css
 [source,css]
 ----
 .calendar-view {