add tmw-related help, do not touch manaplus's

[Helianthella]

NPCs can use @@?|@@ links to open the help window and the help window can display pictures so it is useful to display set-by-step help or tutorials.

examples of what can be done:

• make the candor tutorial link to @@?keys|all hotkeys@@
• make the candor tutorial link to @@?levelup|how to level up@@
• make the candor turorial explain the game interface (inventory, chat, shortcuts, spells, ...)
• make the party creation npc explain the social window
• make a troubleshooting npc to solve the most common problems (in this PR I have put buggy server protection)

we could even go as far as building a quest log hybrid using npc and the help window

I first wanted to modify manaplus's built-in help files but I think it is better to use a subfolder for tmw-related tutorials and help and commit my changes to the main manaplus repo instead of overwriting the files

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requires themanaworld/tmw-tools#13

[wushin]

@4144 @mekolat Whats the status of this?
@Cassy1 what do you think?

[Helianthella]

@wushin it is fully working but it requires themanaworld/tmw-tools#13 to work properly.
I still plan to add more help to it