Add spreadsheet-config-server as a submodule (#4)

Signed-off-by: achour94 <[email protected]>

Author: achour94

.gitmodules

@@ -302,3 +302,7 @@
 	path = backend/libs/filter
 	url = https://github.com/gridsuite/filter
 	branch = main
+[submodule "backend/servers/spreadsheet-config-server"]
+	path = backend/servers/spreadsheet-config-server
+	url = https://github.com/gridsuite/spreadsheet-config-server
+	branch = main

backend/servers/pom.xml

@@ -51,6 +51,7 @@
         <module>security-analysis-server</module>
         <module>sensitivity-analysis-server</module>
         <module>shortcircuit-server</module>
+        <module>spreadsheet-config-server</module>
         <module>study-notification-server</module>
         <module>study-server</module>
         <module>timeseries-server</module>