Some fixes in mark_animations and span command (#355)

Co-authored-by: StraToN <StraToN@users.noreply.github.com>

docs/api/SpawnCommand.md

@@ -0,0 +1,40 @@
+<!-- Auto-generated from JSON by GDScript docs maker. Do not edit this document directly. -->
+
+# SpawnCommand
+
+**Extends:** [ESCBaseCommand](../ESCBaseCommand) < [Node](../Node)
+
+## Description
+
+`spawn path [object2]`
+
+Instances a scene determined by "path", and places in the position of
+object2 (object2 is optional)
+
+@ESC
+
+## Method Descriptions
+
+### configure
+
+```gdscript
+func configure() -> ESCCommandArgumentDescriptor
+```
+
+Return the descriptor of the arguments of this command
+
+### validate
+
+```gdscript
+func validate(arguments: Array)
+```
+
+Validate wether the given arguments match the command descriptor
+
+### run
+
+```gdscript
+func run(command_params: Array) -> int
+```
+
+Run the command