[clang-tools-extra] [clang-tidy][docs] improve documentation on cppcoreguidelines-narrowing-conversions (#111510) (PR #118209)

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@@ -27,6 +27,29 @@ This check will flag:
  - All applications of binary operators with a narrowing conversions.
    For example: ``int i; i+= 0.1;``.
 
+Note that arithmetic with integer types may perform implicit conversions if the used integer types are smaller than ``int``.
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EugeneZelenko wrote:

Please follow 80 characters limit.

https://github.com/llvm/llvm-project/pull/118209