commands/new: Improve theme creation

- Update the skeleton structure to match the new template system.
- Add a --format flag to the `hugo new theme` command to control the
  format of the site configuration and default archetype files.
- Remove theme.toml. This file's presence can be confusing for new
  users, and the README in the themes repository already has an example.
- Remove the LICENSE and README files from the skeleton. These files
  are not needed for a theme to work, and they can be added later by
  the user if desired.

Closes #13489
Closes #13544

create/skeletons/theme/layouts/_partials/head/css.html

@@ -1,5 +1,5 @@
 {{- with resources.Get "css/main.css" }}
-  {{- if eq hugo.Environment "development" }}
+  {{- if hugo.IsDevelopment }}
     <link rel="stylesheet" href="{{ .RelPermalink }}">
   {{- else }}
     {{- with . | minify | fingerprint }}

create/skeletons/theme/layouts/_partials/head/js.html

@@ -0,0 +1,16 @@
+{{- with resources.Get "js/main.js" }}
+  {{- $opts := dict
+    "minify" (not hugo.IsDevelopment)
+    "sourceMap" (cond hugo.IsDevelopment "external" "")
+    "targetPath" "js/main.js"
+  }}
+  {{- with . | js.Build $opts }}
+    {{- if hugo.IsDevelopment }}
+      <script src="{{ .RelPermalink }}"></script>
+    {{- else }}
+      {{- with . | fingerprint }}
+        <script src="{{ .RelPermalink }}" integrity="{{ .Data.Integrity }}" crossorigin="anonymous"></script>
+      {{- end }}
+    {{- end }}
+  {{- end }}
+{{- end }}

create/skeletons/theme/layouts/_partials/menu.html

@@ -18,7 +18,7 @@ Renders a menu for the given menu ID.
   </nav>
 {{- end }}
 
-{{- define "partials/inline/menu/walk.html" }}
+{{- define "_partials/inline/menu/walk.html" }}
   {{- $page := .page }}
   {{- range .menuEntries }}
     {{- $attrs := dict "href" .URL }}

create/skeletons/theme/layouts/partials/head/js.html

@@ -1,12 +0,0 @@
-{{- with resources.Get "js/main.js" }}
-  {{- if eq hugo.Environment "development" }}
-    {{- with . | js.Build }}
-      <script src="{{ .RelPermalink }}"></script>
-    {{- end }}
-  {{- else }}
-    {{- $opts := dict "minify" true }}
-    {{- with . | js.Build $opts | fingerprint }}
-      <script src="{{ .RelPermalink }}" integrity="{{- .Data.Integrity }}" crossorigin="anonymous"></script>
-    {{- end }}
-  {{- end }}
-{{- end }}

create/skeletons/theme/layouts/taxonomy.html

@@ -0,0 +1,7 @@
+{{ define "main" }}
+  <h1>{{ .Title }}</h1>
+  {{ .Content }}
+  {{ range .Pages }}
+    <h2><a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a></h2>
+  {{ end }}
+{{ end }}

create/skeletons/theme/layouts/term.html

@@ -0,0 +1,7 @@
+{{ define "main" }}
+  <h1>{{ .Title }}</h1>
+  {{ .Content }}
+  {{ range .Pages }}
+    <h2><a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a></h2>
+  {{ end }}
+{{ end }}