feat: TemplateList proxy for configuration

Introduce a new proxy TemplateList similar to TemplateDict to handle
list in configuration data structures, both TemplateList and
TemplateDict interplay through the visitation.

Author: fblanchetNaN

incipyt/_internal/dumpers.py

@@ -75,15 +75,13 @@ def dump_in(self, config):
 
 
 class TextFile(BaseDumper):
-    def dump_in(self, config):
-        with self.open() as file:
-            file.write(config[None])
-
+    def __init__(self, path, sep="\n", sanitizer=None):
+        super().__init__(path, sanitizer)
+        self._sep = sep
 
-class Requirement(BaseDumper):
     def dump_in(self, config):
         with self.open() as file:
-            file.write("\n".join(config[None]))
+            file.write(self._sep.join(config) + self._sep)
 
 
 class Toml(BaseDumper):