Add: [Doxygen] Add the current version of documentation in header (#7940)

While at it, renamed the project names to reflect how we currently
refer to them.

Doxyfile

@@ -7,8 +7,8 @@
 # Project related configuration options
 #---------------------------------------------------------------------------
 DOXYFILE_ENCODING      = UTF-8
-PROJECT_NAME           = OpenTTD
-PROJECT_NUMBER         =
+PROJECT_NAME           = "OpenTTD Source"
+PROJECT_NUMBER         = $(VERSION)
 PROJECT_BRIEF          =
 PROJECT_LOGO           =
 OUTPUT_DIRECTORY       = docs/source/

src/script/api/Doxyfile_AI

@@ -9,8 +9,8 @@
 # Project related configuration options
 #---------------------------------------------------------------------------
 DOXYFILE_ENCODING      = UTF-8
-PROJECT_NAME           = "OpenTTD NoAI API"
-PROJECT_NUMBER         =
+PROJECT_NAME           = "OpenTTD AI API"
+PROJECT_NUMBER         = $(VERSION)
 OUTPUT_DIRECTORY       = ../../../docs/aidocs/
 CREATE_SUBDIRS         = NO
 OUTPUT_LANGUAGE        = English

src/script/api/Doxyfile_Game

@@ -9,8 +9,8 @@
 # Project related configuration options
 #---------------------------------------------------------------------------
 DOXYFILE_ENCODING      = UTF-8
-PROJECT_NAME           = "OpenTTD Game API"
-PROJECT_NUMBER         =
+PROJECT_NAME           = "OpenTTD GameScript API"
+PROJECT_NUMBER         = $(VERSION)
 OUTPUT_DIRECTORY       = ../../../docs/gamedocs/
 CREATE_SUBDIRS         = NO
 OUTPUT_LANGUAGE        = English