add missing untranslated functions in japanese

Author: superruzafa

content/ja/functions/exists.md

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+---
+title: exists
+untranslated: true
+---
+
+# `exists`
+
+{{< signature exists >}}
+
+`exists` checks whether at least one element in this collection satisfy the predicate `p`, returning `true` if such element exists.
+
+{{< figure src="images/functions/exists.svg" >}}
+
+On empty collections the predicate `p` cannot be satisfied at least once, hence this function returns `false`.
+
+{{< figure src="images/functions/exists.2.svg" >}}

content/ja/functions/forall.md

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+---
+title: forall
+untranslated: true
+---
+
+# `forall`
+
+{{< signature forall >}}
+
+`forall` checks whether all elements in this collection satisfy the predicate `p`, returning `false` if `p` doesn't stand for at least one element.
+
+{{< figure src="images/functions/forall.svg" >}}
+
+On empty collections there is no element which doesn't satisfy `p`, hence this function returns `true`.
+
+{{< figure src="images/functions/forall.2.svg" >}}

content/ja/functions/lift.md

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+---
+title: lift
+untranslated: true
+---
+
+# `lift`
+
+{{< signature lift >}}
+
+`lift` creates an anonymous function that wraps with `Some` the value returned by this partial function if it's defined for the given input value.
+
+{{< figure src="images/functions/lift.svg" >}}
+
+For those input values for which this partial function is not defined, the anonymous function will return `None`.
+
+{{< figure src="images/functions/lift.2.svg" >}}

content/ja/functions/runWith.md

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+---
+title: runWith
+untranslated: true
+---
+
+# `runWith`
+
+{{< signature runWith >}}
+
+`runWith` creates an anonymous function that applies this partial function and then `g` to an input value, if this partial function is defined for such value, and returns `true`.
+
+{{< figure src="images/functions/runWith.svg" >}}
+
+For those values this partial function is not defined, the anonymous function just return false, without even applying `g`.
+
+{{< figure src="images/functions/runWith.2.svg" >}}

content/ja/functions/unlift.md

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+---
+title: unlift
+untranslated: true
+---
+
+# `unlift`
+
+{{< signature unlift >}}
+
+`unlift` creates an anonymous partial function that returns the value extracted
+from `Some` returned by the function `f`.
+
+{{< figure src="images/functions/unlift.svg" >}}
+
+If `f` returns `None` then the anonymous partial function will throw a
+`MatchError` exception.
+
+{{< figure src="images/functions/unlift.2.svg" >}}
+