Merge pull request #18 from G-e-n-e-v-e-n-s-i-S/file-exists

Add exists_in_package script function

doc/function/exists_in_package.txt

@@ -0,0 +1,13 @@
+Function: exists_in_package
+
+--Usage--
+> exists_in_package("/package/filename")
+
+Check if a file exists in a given package.
+
+--Parameters--
+! Parameter	Type			Description
+| @input@	[[type:string]]		Path of the file, starting from the data directory.
+
+--Examples--
+> exists_in_package("/magic-modules.mse-include/watermarks/custom_user_watermark.png")  ==  true

doc/function/index.txt

@@ -113,3 +113,4 @@ These functions are built into the program, other [[type:function]]s can be defi
 | [[fun:assert]]		Check a condition for debugging purposes.
 | [[fun:warning]]		Output a warning message.
 | [[fun:error]]			Output an error message.
+| [[fun:exists_in_package]]			Checks if a file exists in a package.