[Draft] Game Modes structure

[RaikireHiuduo]

This is a draft for #143 .

If nobody comments by Wednesday, I might consider to deal with Game_Modes (main four only).

If I did not finish by the end of February unless stated otherwise, assume all my PRs went stale.

# {Game Mode title}
## Introduction
{Either take FAQ explanation or the game mode description, whichever made more sense and complete}

It should roughly answer: What is this?, quick history if available (the original if emulation like osu! or Taiko), when it was implemented

## Hitobjects
{Can probably just take FAQ wholesale. For osu!, make sure sliderbreak was mentioned.}

### Playfield
### {Hitcircles}
### {Sliders}
### {Spinners}
### {special gimmick, one gimmick one header}

## Control
{Can probably just take FAQ wholesale, except osu!mania; just need to clean up osu!mania table}

### Play style
(Probably can be removed because it is subjective?)

## Scoring and Grade
{Take from the Score page, and Grade requirement}

## Skin elements
(A link to its Skinning, only)

## Beatmapping
(?)

## Trivia
Dump whatever pointless stuffs that will not help much but cool nevertheless.

[TPGPL]

Playstyles can be taken from /wiki/Play_Styles (or just delete this header)