Infrastructure should include issue templates #13

Discussed in #14

From the discussion:

• Epic: A collection of related work
  • The title should be extremely simple, e.g. "Self-Hosting", "Parser", or "LLVM"
  • It will likely map to a workspace in our monorepo. If not, there might need to be an issue type for our workspaces
• Feature or User Story: A thing the project should be able to do, an activity the user will be able to perform with the product
  • The title should be a "should" statement, e.g. "The parser should handle function calls"
  • It will likely map to a test suite
• Task: A generic unit of work
  • The title should be phrased as if it was a commit, i.e. a short, present-tense, imperative sentence describing what work should be done
  • It will likely map to one or more commits
• Bug: A divergence between required and actual behavior, and tracks the work done to correct the defect and verify the correction
  • The title should be a "should" statement with an "instead" clause, e.g. "The parser should handle function calls instead of throwing an error"
  • It will likely not map to anything specific
  • It should always be linked to a Feature/User Story
• Issue or Problem: A problem that is not a bug, or some other obstacle to progress
  • The title likely won't have much structure
  • It will likely not map to anything specific
  • It should always be linked to another work item (of any type)