[zserge-webview] Add new port (#6239)

* [webview] Add new port

* [zserge-webview] Update to 2019-04-27

* [zserge-webview] Fix Linux, macOS support

ports/zserge-webview/CONTROL

@@ -0,0 +1,3 @@
+Source: zserge-webview
+Version: 2019-04-27-1
+Description: Tiny cross-platform webview library for C/C++/Golang.

ports/zserge-webview/portfile.cmake

@@ -0,0 +1,58 @@
+# header-only library
+
+include(vcpkg_common_functions)
+
+vcpkg_from_github(
+    OUT_SOURCE_PATH SOURCE_PATH
+    REPO zserge/webview
+    REF 16c93bcaeaeb6aa7bb5a1432de3bef0b9ecc44f3
+    SHA512 153824bd444eafe6cc5ae00800422b41d4047dc85a164c465990c3be06d82003b532e1e869bb40e3a77cbe4789ff970fcda50ef00ac7b3e2f22ef3f566340026
+    HEAD_REF master
+)
+
+file(COPY ${SOURCE_PATH}/webview.h DESTINATION ${CURRENT_PACKAGES_DIR}/include)
+
+set(WEBVIEW_GTK "0")
+set(WEBVIEW_WINAPI "0")
+set(WEBVIEW_COCOA "0")
+
+if(WIN32)
+    set(WEBVIEW_WINAPI "1")
+elseif(UNIX)
+    if(APPLE)
+        set(WEBVIEW_COCOA "1")
+    else()
+        set(WEBVIEW_GTK "1")
+    endif()
+endif()
+
+file(READ ${CURRENT_PACKAGES_DIR}/include/webview.h _contents)
+string(REPLACE
+    "#ifdef WEBVIEW_STATIC"
+    "#if 1 // #ifdef WEBVIEW_STATIC"
+    _contents "${_contents}"
+)
+string(REPLACE
+    "#ifdef WEBVIEW_IMPLEMENTATION"
+    "#if 1 // #ifdef WEBVIEW_IMPLEMENTATION"
+    _contents "${_contents}"
+)
+string(REPLACE
+    "defined(WEBVIEW_GTK)"
+    "${WEBVIEW_GTK} // defined(WEBVIEW_GTK)"
+    _contents "${_contents}"
+)
+string(REPLACE
+    "defined(WEBVIEW_WINAPI)"
+    "${WEBVIEW_WINAPI} // defined(WEBVIEW_WINAPI)"
+    _contents "${_contents}"
+)
+string(REPLACE
+    "defined(WEBVIEW_COCOA)"
+    "${WEBVIEW_COCOA} // defined(WEBVIEW_COCOA)"
+    _contents "${_contents}"
+)
+file(WRITE ${CURRENT_PACKAGES_DIR}/include/webview.h "${_contents}")
+
+# Handle copyright
+configure_file(${SOURCE_PATH}/LICENSE ${CURRENT_PACKAGES_DIR}/share/${PORT}/copyright COPYONLY)