Add an alias library to Cmake

Lets people building in-tree to link against the same target as people using find_package.

Author: sum01

CMakeLists.txt

@@ -19,6 +19,9 @@ find_package(ZLIB QUIET)
 include(GNUInstallDirs)
 
 add_library(${PROJECT_NAME} INTERFACE)
+# Lets you address the target with httplib::httplib
+# Only useful if building in-tree, versus using it from an installation.
+add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
 
 # Might be missing some, but this list is somewhat comprehensive
 target_compile_features(${PROJECT_NAME} INTERFACE