add doc/*/scripting/builtins/libbase64.md

doc/en/scripting/builtins/libbase64.md

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+# *base64* library
+
+Library for base64 encoding/decoding.
+
+```lua
+-- Encode bytes to base64 string
+base64.encode(bytes: table|ByteArray) -> str
+
+-- Decode base64 string to ByteArray or lua table if second argument is set to true
+base64.decode(base64string: str, [optional]usetable: bool=false) -> table|ByteArray
+```