Beaver Species

[SightglassCat]

• What is the purpose of the pull request?
  Adds a Beaver race to the game. Contains only 1 subspecies.
• Give a brief description of what you changed or added.
  New race: Beaver (1 subspecies)
  New TF Item: Maple Bar
  New Attribute Item: Maple Mocha
• Are any new graphical assets required?
  Species icon and item icons are included.
• Has this change been tested? If so, mention the version number that the test was based on.
  Tested on 0.4.7.5
• So we have a better idea of who you are, what is your Discord Handle?
  Sightglass#1408

[DSGMods]

Please run all of your SVGs through SVGO to reduce filesize. Instructions are pinned to #mod-discussion.