feat: replace ui_search_placeholder with docsy provided ui_search

Author: SayakMukhopadhyay

content/en/docs/contribute/localization.md

@@ -450,7 +450,7 @@ translate the value of each string. For example, this is the German-language
 placeholder text for the search form:
 
 ```toml
-[ui_search_placeholder]
+[ui_search]
 other = "Suchen"
 ```
 

i18n/en/en.toml

@@ -648,7 +648,7 @@ other = "Copied to clipboard: "
 [translated_by]
 other = "Translated By"
 
-[ui_search_placeholder]
+[ui_search]
 other = "Search this site"
 
 [version_check_mustbe]

layouts/partials/search-input-custom.html

@@ -2,6 +2,14 @@
 {{ $lang := .Site.Language.Lang }}
 {{ $searchFile := printf "content/%s/search.md" $lang }}
 
+{{ $check := "" }}
+{{ if T "ui_search_placeholder" }}
+{{ warnf "The search bar placeholder for the language %s is using a custom \"ui_search_placeholder\" key. Please change the key in the translations to the Docsy provided \"ui_search\"." $lang }}
+{{ $check = T "ui_search_placeholder" }}
+{{ else }}
+{{ $check = T "ui_search" }}
+{{ end }}
+
 <div class="search-bar">
   <i class="search-icon fa-solid fa-search"></i>
   <input
@@ -13,8 +21,8 @@
     data-search-page="{{ "search/" | relURL }}"
     {{ end }}
     class="search-input td-search-input"
-    placeholder="{{ T "ui_search_placeholder" }}"
-    aria-label="{{ T "ui_search_placeholder" }}"
+    placeholder="{{ $check }}"
+    aria-label="{{ $check }}"
     autocomplete="off"
   >
 </div>