docs: Prepare for new sub tree

See #11925

docs/content/en/functions/os/FileExists.md

@@ -1,41 +0,0 @@
----
-title: os.FileExists
-description: Reports whether the file or directory exists.
-categories: []
-keywords: []
-action:
-  aliases: [fileExists]
-  related:
-    - functions/os/Getenv
-    - functions/os/ReadDir
-    - functions/os/ReadFile
-    - functions/os/Stat
-  returnType: bool
-  signatures: [os.FileExists PATH]
-aliases: [/functions/fileexists]
----
-
-The `os.FileExists` function attempts to resolve the path relative to the root of your project directory. If a matching file or directory is not found, it will attempt to resolve the path relative to the [`contentDir`](/getting-started/configuration#contentdir). A leading path separator (`/`) is optional.
-
-With this directory structure:
-
-```text
-content/
-├── about.md
-├── contact.md
-└── news/
-    ├── article-1.md
-    └── article-2.md
-```
-
-The function returns these values:
-
-```go-html-template
-{{ fileExists "content" }} → true
-{{ fileExists "content/news" }} → true
-{{ fileExists "content/news/article-1" }} → false
-{{ fileExists "content/news/article-1.md" }} → true
-{{ fileExists "news" }} → true
-{{ fileExists "news/article-1" }} → false
-{{ fileExists "news/article-1.md" }} → true
-```