Add port for imgui library

ports/imgui/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.8)
+project(imgui CXX)
+
+find_path(STB_INCLUDE_DIR stb_rect_pack.h stb_textedit.h stb_truetype.h)
+
+set(IMGUI_INCLUDES_PUBLIC
+    imgui.h
+    imconfig.h
+)
+
+set(IMGUI_INCLUDES_PRIVATE
+    imgui_internal.h
+)
+
+set(IMGUI_SOURCES
+    imgui.cpp
+    imgui_demo.cpp
+    imgui_draw.cpp
+)
+
+add_library(imgui STATIC
+    ${IMGUI_INCLUDES_PUBLIC}
+    ${IMGUI_INCLUDES_PRIVATE}
+    ${IMGUI_SOURCES}
+)
+
+target_include_directories(imgui
+    PRIVATE
+    ${IMGUI_INCLUDES_PRIVATE}
+    ${STB_INCLUDE_DIR}
+
+    PUBLIC
+    ${IMGUI_INCLUDES_PUBLIC}
+)
+
+install(TARGETS imgui
+    ARCHIVE DESTINATION lib
+)
+
+if(NOT IMGUI_SKIP_HEADERS)
+    install(
+        FILES ${IMGUI_INCLUDES_PUBLIC}
+        DESTINATION include
+    )
+endif()

ports/imgui/CONTROL

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+Source: imgui
+Version: 1.51
+Build-Depends: stb (windows)
+Description: Bloat-free Immediate Mode Graphical User interface for C++ with minimal dependencies.

ports/imgui/portfile.cmake

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+include(vcpkg_common_functions)
+set(SOURCE_PATH ${CURRENT_BUILDTREES_DIR}/src/imgui-1.51)
+vcpkg_download_distfile(ARCHIVE
+    URLS "https://github.com/ocornut/imgui/archive/v1.51.zip"
+    FILENAME "imgui-1.51.zip"
+    SHA512 a3c77887396991f8371c0cf5b42d781d758877cdb194a7c6ea8b34939f4b300f55f176d601dd0e167ea2a20bd8a47b958ad1bca16864a19c1cc9b2c7a889ab29
+)
+vcpkg_extract_source_archive(${ARCHIVE})
+
+file(COPY ${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt DESTINATION ${SOURCE_PATH})
+
+vcpkg_configure_cmake(
+    SOURCE_PATH ${SOURCE_PATH}
+    PREFER_NINJA
+    OPTIONS_DEBUG
+        -DIMGUI_SKIP_HEADERS=ON
+)
+
+vcpkg_install_cmake()
+vcpkg_copy_pdbs()
+
+file(COPY ${SOURCE_PATH}/LICENSE.txt DESTINATION ${CURRENT_PACKAGES_DIR}/share/imgui)
+file(RENAME ${CURRENT_PACKAGES_DIR}/share/imgui/LICENSE.txt ${CURRENT_PACKAGES_DIR}/share/imgui/copyright)