LibHTML: Start building a simple code generator for CSS properties

Code for parsing and stringifying CSS properties is now generated based
on LibHTML/CSS/Properties.json

At the moment, the file tells us three things:

- The name of a property
- Its initial value
- Whether it's inherited

Also, for shorthand properties, it provides a list of all the longhand
properties it may expand too. This is not actually used in the engine
yet though.

This *finally* makes layout tree dumps show the names of CSS properties
in effect, instead of "CSS::PropertyID(32)" and such. :^)

Libraries/LibHTML/CodeGenerators/Generate_CSS_PropertyID_cpp/Makefile

@@ -0,0 +1,33 @@
+PROGRAM = Generate_CSS_PropertyID_cpp
+
+OBJS = \
+    Generate_CSS_PropertyID_cpp.o \
+    $(SERENITY_ROOT)/AK/String.o \
+    $(SERENITY_ROOT)/AK/StringImpl.o \
+    $(SERENITY_ROOT)/AK/StringBuilder.o \
+    $(SERENITY_ROOT)/AK/StringView.o \
+    $(SERENITY_ROOT)/AK/JsonValue.o \
+    $(SERENITY_ROOT)/AK/JsonParser.o \
+    $(SERENITY_ROOT)/AK/LogStream.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CIODevice.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CFile.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CObject.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CEvent.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CSocket.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CLocalSocket.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CNotifier.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CLocalServer.o \
+    $(SERENITY_ROOT)/Libraries/LibCore/CEventLoop.o
+
+all: $(PROGRAM)
+
+CXXFLAGS = -std=c++17 -Wall -Wextra
+
+%.o: %.cpp
+	$(PRE_CXX) $(CXX) $(CXXFLAGS) -I../ -I$(SERENITY_ROOT)/ -I$(SERENITY_ROOT)/Libraries/ -o $@ -c $<
+
+$(PROGRAM): $(OBJS)
+	$(CXX) $(LDFLAGS) -I../ -I$(SERENITY_ROOT)/ -I$(SERENITY_ROOT)/Libraries/ -o $(PROGRAM) $(OBJS)
+
+clean:
+	rm -f $(PROGRAM) $(OBJS)