Fix primary RaisedButton text color in DarkTheme

newIDE/app/src/MainFrame/Editors/StartPage/__snapshots__/StartPage.spec.js.snap

@@ -160,7 +160,7 @@ exports[`StartPage renders the start page with a project 1`] = `
                 <span
                   style={
                     Object {
-                      "color": "#ffffff",
+                      "color": "white",
                       "fontSize": 14,
                       "fontWeight": 500,
                       "letterSpacing": 0,
@@ -832,7 +832,7 @@ exports[`StartPage renders the start page with no project opened 1`] = `
                 <span
                   style={
                     Object {
-                      "color": "#ffffff",
+                      "color": "white",
                       "fontSize": 14,
                       "fontWeight": 500,
                       "letterSpacing": 0,

newIDE/app/src/UI/Theme/DarkTheme/index.js

@@ -65,6 +65,9 @@ const theme: Theme = {
   stepper: {
     textColor: lightWhite,
   },
+  raisedButton: {
+    primaryTextColor: notSoWhite,
+  },
 
   // GDevelop specific variables:
   closableTabs: {

newIDE/app/src/UI/Theme/DefaultTheme/index.js

@@ -50,6 +50,9 @@ const theme = {
     actionColor: gdevelopLightBlue,
   },
   stepper: {},
+  raisedButton: {
+    primaryTextColor: 'white',
+  },
 
   // GDevelop specific variables:
   closableTabs: {