Fix missing cstdint include

While trying to compile quill v1.7 I have encountered a compiler error.

Executing following series of commands

$ mkdir cmake_build
$ cd cmake_build/
$ cmake -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_BUILD_TYPE=Release ..

Results in following error:

<path/to/quill>/quill/include/quill/detail/misc/Common.h:63:6: warning: elaborated-type-specifier for a scoped enum must not use the ‘class’ keyword
   63 | enum class Timezone : uint8_t
      | ~~~~ ^~~~~
      |      -----
<path/to/quill>/quill/include/quill/detail/misc/Common.h:63:21: error: found ‘:’ in nested-name-specifier, expected ‘::’
   63 | enum class Timezone : uint8_t
      |                     ^
      |                     ::

Compiler version:

$ /usr/bin/c++  --version
c++ (GCC) 13.2.1 20240316 (Red Hat 13.2.1-7)
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

This error seems to be triggered by missing include of cstdint. Since enum class is using uint8_t it would reasonable to expect that cstdint header has to be included directly.

odygrd / quill

Fix missing cstdint include #416