Add dplyr to Imports and initialize variables

Added dplyr (>= 1.1.4) to the Imports in DESCRIPTION. Initialized several variables to NULL in outputs_simulations_settings.

Author: MathieuDepetris

DESCRIPTION

@@ -17,6 +17,7 @@ RoxygenNote: 7.3.3
 URL: https://github.com/umr-marbec/isisinsight, https://umr-marbec.github.io/isisinsight/
 BugReports: https://github.com/umr-marbec/isisinsight/issues
 Imports: 
+    dplyr (>= 1.1.4),
     lifecycle,
     lubridate (>= 1.9.4),
     magrittr,

R/outputs_simulations_settings.R

@@ -10,6 +10,13 @@
 #'
 outputs_simulations_settings <- function(directory_path) {
   # 1 - Global variable assignment ----
+  population <- NULL
+  scenario_name <- NULL
+  step <- NULL
+  value <- NULL
+  year <- NULL
+  zone_population <- NULL
+  simulation_name <- NULL
   # Empty for now
   # 2 - Global argument check ----
   if (missing(x = directory_path)