Skill Framework improvements

[Asmotym]

Hi @aedenthorn,

It's been some time, but as we discussed last time, I've been working on adding a few features to the Skill Framework.
I added a README to detail how to use the new features I added / changes I hope that it can help understand what changed.

As mentioned in the README, you can take a look here at my WIP skills using the new modifications.

Here is a quick list of changes:

• Added a BaseSkill class to be extended by newly created skills
• Improving base plugin code by reformatting the code & adding comments
• Adding SkillCategories class to add static constants to ease understanding the skill screen categories ID
• Update SkillInfo to add delegates that are called in Harmony patches to ease the creation of some skills

It's better to mention that it's probably not compatible with mods that use an older version of this framework. I tested on two skills:

• Second Wind Skill (not from you)
• MovementSpeedSkill (from you)

These aren't working with the new version and I wasn't able to identify why for now (I've not spent much time on it)

Of course, I'm available to discuss, review, change & debug things (here or on Discord) if you need.
Thanks!