put generated julia component files in src/jl

- so that their paths never conflict with the julia module file
  in case-insensitive filesystems
- this also makes the src directory less noisy (especially for
  devs that do not care about julia)

dash/development/_jl_components_generation.py

@@ -91,7 +91,7 @@
     "DashBase": "0.1",
 }
 
-jl_component_include_string = 'include("{name}.jl")'
+jl_component_include_string = 'include("jl/{name}.jl")'
 
 jl_resource_tuple_string = """DashBase.Resource(
     relative_package_path = {relative_package_path},
@@ -500,7 +500,11 @@ def generate_struct_file(name, props, description, project_shortname, prefix):
 
     file_name = format_fn_name(prefix, name) + ".jl"
 
-    file_path = os.path.join("src", file_name)
+    # put component files in src/jl subdir
+    if not os.path.exists("src/jl"):
+        os.makedirs("src/jl")
+
+    file_path = os.path.join("src", "jl", file_name)
     with open(file_path, "w") as f:
         f.write(import_string)
         f.write(class_string)