Load towers dynamically

[olistic]

This adds support for community towers, as well as official towers that don't ship with the game. WarriorJS CLI searches for towers (@warriorjs/tower-* and warriorjs-tower-*) in the nearest parent node_modules directory. This should work for both global and local installations of the CLI.

Closes #100 Fixes #168

[codecov-io]

Codecov Report

Merging #169 into master will increase coverage by 0.15%. The diff coverage is 89.58%.

@@            Coverage Diff             @@
##           master     #169      +/-   ##
==========================================
+ Coverage   92.19%   92.35%   +0.15%     
==========================================
  Files          83       85       +2     
  Lines        1051     1072      +21     
  Branches      177      179       +2     
==========================================
+ Hits          969      990      +21     
  Misses         67       67              
  Partials       15       15

Impacted Files	Coverage Δ
packages/warriorjs-cli/src/loadTowers.js	100% <100%> (ø)
packages/warriorjs-cli/src/Tower.js	100% <100%> (ø)	:arrow_up:
packages/warriorjs-cli/src/Profile.js	96.36% <100%> (+0.06%)	:arrow_up:
packages/warriorjs-cli/src/utils/getLevelConfig.js	100% <100%> (ø)	:arrow_up:
packages/warriorjs-cli/src/utils/getTowerId.js	100% <100%> (ø)
packages/warriorjs-cli/src/Game.js	52.63% <68.75%> (+1.28%)	:arrow_up:

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