New update, balance and some reworks

This new changes are focused in making some weapons more flashed out and sometimes more powerfull, as well making them a little more interesting and fun to use. Playing in extreme difficulty now seems a little more balanced around some specific places. Shorting out some boring boss phases. New game cover and header for the new steam library.

Detailed changes are as follows:

• New Checkpoint added to fourth stage, it was only one before (hope this makes things less tiring in extreme difficulty).

• Mini Aliens that appear in extreme difficulty, doesnt do damage anymore, but they push more on impact.

• Life and energy UI are reduced in size for those who are playing for the first time.

• There was a bug with lasers after level 3, specifically if playing with controller, that made lasers aim wrong. (fixed now).

• In The stage "The Void", in the last part before the first checkpoint, laser ships dosnt come with shields anymore in the extreme difficulty. (Yeah yeah, it was unfair as ****).

• Changed how ultima drone works, it spawns instantly regardless upgrade level, and it always shot coming from the ship.

• * Ultima drone with lasers, is stronger now, follwing "secundary weapons laser" level, x4.

• * Also, ultima drone witrh lasers, last 50 ticks longer (about 1 second).

• Second boss, blackhole part, time reduced from 90 to 45 seconds.

• Shotgun reworked (and buffed)

• * Shotgun projectiles goes through the end of the screen, they dosnt disappear anymore.

• * Fifth upgrade removed, now it increases projectile speed.

• * Initial bullet spread radius reduced from 100 to 80, and -14 per level.

• Third boss, where the head stay centered, life reduced from 200 to 80.