Add util function to evaluate template expressions

[EricKarschner37]

• Add a util function to evaluate template expressions of the form ${expression}
  • Supports basic arithmetic (addition, subtraction, multiplication, and division) and Math.abs()
  • Respects order of operations (including evaluating expressions in (parentheses) first.
  • Accepts an optional obj parameter to support variable lookup: replaceTemplateVars("${var}", { var: 5 }) === "5"
• Add the jest module for testing, as well as some basic configuration

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