Add _Show about microlens HOT 4 CLOSED

I will accept a PR that adds this (the traversal must also have haddocks on par with other microlens docs).

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btw it is very easy to implement. But in what cases is it useful? Show and Read are simple classes for debugging.

import Text.Read (readMaybe)

_Show :: (Show a, Read a) => Traversal' String a
_Show next source =
  case readMaybe source of
    Just value -> show <$> next value
    Nothing -> pure source

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@kana-sama Here's a use case: https://hackage.haskell.org/package/pcre2-1.1.4/docs/Text-Regex-Pcre2.html#v:_regex

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sjshuck@7a816f1

I didn't bump versions because of another couple functions I remembered to ask about that you might want to include in the same release, if at all (see above issue).

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