cipher: add page (#3285)

pages/windows/cipher.md

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+# cipher
+
+> Encrypt or decrypt files on NTFS drives.
+
+- Encrypt a file or directory:
+
+`cipher /e:{{path/to/file_or_directory}}`
+
+- Decrypt a file or directory:
+
+`cipher /d:{{path/to/file_or_directory}}`
+
+- Securely remove a file or directory:
+
+`cipher /w:{{path/to/file_or_directory}}`