rename(doc): renamed @type -> @filetype

docs/language.md

@@ -501,17 +501,17 @@ key = "foo"
 Built-in key pattern is a pattern to access values integrated with a transpiler,
 starts with a commercial at (`@`, `U+0040`),
 
-- `@output` ... A [string](#string) to specify destination path to output a
+- `@output`  ... A [string](#string) to specify destination path to output a
  transpiled source. Write only.
-- `@type`  ... A [string](#string) to specify file type to transpile.
- Supported file types are described
- [here](#supported-file-types). Write only. (Normally infered
- from `@output` and not needed.)
-- `@nan` ... A [float](#float) expresses quiet "Not a Number". Read only.
-- `@inf` ... A [float](#float) expresses positive infinity. Read only.
-- `@true` ... A [boolean](#boolean) expresses true. Read only.
-- `@false` ... A [boolean](#boolean) expresses false. Read only.
-- `@null` ... A [null](#null) value. Read only.
+- `@filetype` ... A [string](#string) to specify file type to transpile.
+  Supported file types are described
+  [here](#supported-file-types). Write only. (Normally infered
+  from `@output` and not needed.)
+- `@nan`  ... A [float](#float) expresses quiet "Not a Number". Read only.
+- `@inf`  ... A [float](#float) expresses positive infinity. Read only.
+- `@true`  ... A [boolean](#boolean) expresses true. Read only.
+- `@false`  ... A [boolean](#boolean) expresses false. Read only.
+- `@null`  ... A [null](#null) value. Read only.
 
 Note that these values are file-specific, and independent from the root
 scope.