Document new predefined variable ${columnNumber} (#8009)

* Add example for predefined variable `${fileDirnameBasename}`

* Docu new predefined variable `${columnNumber}`

See https://code.visualstudio.com/updates/v1_97#_column-number-variable.

Author: muzimuzhi

docs/editor/variables-reference.md

@@ -29,6 +29,7 @@ The following predefined variables are supported:
 - **${fileDirnameBasename}** - the current opened file's folder name
 - **${cwd}** - the task runner's current working directory upon the startup of VS Code
 - **${lineNumber}** - the current selected line number in the active file
+- **${columnNumber}** - the current selected column number in the active file
 - **${selectedText}** - the current selected text in the active file
 - **${execPath}** - the path to the running VS Code executable
 - **${defaultBuildTask}** - the name of the default build task
@@ -53,9 +54,11 @@ So you will have the following values for each variable:
 - **${relativeFileDirname}** - `folder`
 - **${fileBasename}** - `file.ext`
 - **${fileBasenameNoExtension}** - `file`
-- **${fileDirname}** - `/home/your-username/your-project/folder`
 - **${fileExtname}** - `.ext`
+- **${fileDirname}** - `/home/your-username/your-project/folder`
+- **${fileDirnameBasename}** - `folder`
 - **${lineNumber}** - line number of the cursor
+- **${columnNumber}** - column number of the cursor
 - **${selectedText}** - text selected in your code editor
 - **${execPath}** - location of Code.exe
 - **${pathSeparator}** - `/` on macOS or linux, `\` on Windows