fix: Hugo language related deprecation (v0.158.0+) (#1334)

* language related deprecation fix

Reference: https://github.com/gohugoio/hugo/releases/tag/v0.158.0
.Site.LanguageCode -> .Site.Language.Locale
.Language.LanguageDirection -> .Language.Direction
.Language.LanguageCode -> .Language.Locale

Also, in the configuration hugo.toml, the user should change `languageCode` to `locale`.

* Update languageCode to locale in configuration

* fix(languages): update languageName to label in languages.toml

* .Language.LanguageName -> .Language.Label

* .Language.Lang -> .Language.Name

---------

Co-authored-by: Jimmy Cai <jimmy@cai.im>

demo/config/_default/languages.toml

@@ -1,31 +1,31 @@
 [en]
-    languageName = "English"
-    title        = "Hugo Theme Stack"
-    weight       = 1
+    label  = "English"
+    title  = "Hugo Theme Stack"
+    weight = 1
 
     [en.params.sidebar]
         subtitle = "Card-style Hugo theme designed for bloggers"
 
 [zh]
-    languageName = "简体中文"
-    title        = "Hugo 主题 Stack"
-    weight       = 2
+    label  = "简体中文"
+    title  = "Hugo 主题 Stack"
+    weight = 2
 
     [zh.params.sidebar]
         subtitle = "为博客设计的卡片式 Hugo 主题"
 
 [zh-hant-tw]
-    languageName = "正體中文"
-    title        = "Hugo 主題 Stack"
-    weight       = 3
+    label  = "正體中文"
+    title  = "Hugo 主題 Stack"
+    weight = 3
 
     [zh-hant-tw.params.sidebar]
         subtitle = "為博客設計的卡片式 Hugo 主題"
 
 [ja]
-    languageName = "日本語"
-    title        = "Hugo Theme Stack"
-    weight       = 4
+    label  = "日本語"
+    title  = "Hugo Theme Stack"
+    weight = 4
 
     [ja.params.sidebar]
         subtitle = "ブログ用のカードスタイルの Hugo テーマ"