chore: normalize on 2-space indent & roll out eslint (#791)

In a long overdue sweep on the code style standards, added and
configured `eslint` for TypeScript with minimal settings to guarantee
some minimal degree of homogeneity throughout the codebase. The rule set
is likely to expand over time as we iterate and discover more items we
can and want to enforce.

eslint-config.yaml

@@ -0,0 +1,216 @@
+---
+env:
+  jest: true
+  node: true
+
+plugins:
+  - '@typescript-eslint'
+
+parser: '@typescript-eslint/parser'
+parserOptions:
+  ecmaVersion: 2018
+  sourceType: module
+  project: tsconfig.json
+
+extends:
+  - eslint:recommended
+  - plugin:@typescript-eslint/eslint-recommended
+  - plugin:@typescript-eslint/recommended
+  - plugin:@typescript-eslint/recommended-requiring-type-checking
+
+rules:
+  # Custom Configurations
+
+  '@typescript-eslint/array-type':
+    - error
+    - default: array-simple
+      readonly: array-simple
+
+  '@typescript-eslint/await-thenable':
+    - error
+
+  '@typescript-eslint/brace-style':
+    - error
+    - 1tbs # One True Brace Style!
+    - allowSingleLine: true
+
+  '@typescript-eslint/explicit-member-accessibility':
+    - error
+
+  '@typescript-eslint/indent':
+    - error
+    - 2
+
+  '@typescript-eslint/member-delimiter-style':
+    - error
+    - multiline:
+        delimiter: semi
+        requireLast: true
+      singleline:
+        delimiter: comma
+        requireLast: false
+
+  '@typescript-eslint/member-ordering':
+    - warn
+    - default:
+      - static-field
+      - static-method
+      - instance-field
+      - constructor
+      - instance-method
+
+  '@typescript-eslint/no-empty-function':
+    - error
+    - allow: [constructors]
+
+  '@typescript-eslint/no-extra-parens':
+    - error
+    - all
+    - conditionalAssign: false
+      nestedBinaryExpressions: false
+
+  '@typescript-eslint/no-floating-promises':
+    - error
+
+  '@typescript-eslint/no-for-in-array':
+    - error
+
+  '@typescript-eslint/no-unused-vars':
+    - error
+    - args: all
+      argsIgnorePattern: ^_
+      caughtErrors: all
+      vars: all
+      varsIgnorePattern: ^_
+
+  '@typescript-eslint/no-useless-constructor':
+    - error
+
+  '@typescript-eslint/prefer-for-of':
+    - error
+
+  '@typescript-eslint/prefer-readonly':
+    - error
+
+  '@typescript-eslint/promise-function-async':
+    - error
+    - checkArrowFunctions: false
+
+  '@typescript-eslint/quotes':
+    - error
+    - single
+    - avoidEscape: true
+      allowTemplateLiterals: false
+
+  '@typescript-eslint/require-await':
+    - error
+
+  '@typescript-eslint/type-annotation-spacing':
+    - error
+
+  'array-bracket-spacing':
+    - error
+    - never
+
+  'complexity':
+    - warn
+    - 20
+
+  'consistent-return':
+    - error
+
+  'curly':
+    - error
+    - all
+
+  'dot-location':
+    - error
+    - property
+
+  'dot-notation':
+    - error
+
+  'eqeqeq':
+    - error
+    - always
+    - null: ignore
+
+  'max-len':
+    - error
+    - code: 150
+      ignoreStrings: true
+      ignoreTemplateLiterals: true
+      tabWidth: 2
+
+  'no-alert':
+    - error
+
+  'no-await-in-loop':
+    - warn
+
+  'no-caller':
+    - error
+
+  'no-else-return':
+    - error
+    - allowElseIf: true
+
+  'no-eval':
+    - error
+
+  'no-extra-bind':
+    - warn
+
+  'no-implied-eval':
+    - error
+
+  'no-lone-blocks':
+    - error
+
+  'no-multi-spaces':
+    - error
+    - ignoreEOLComments: true
+
+  'no-new-symbol':
+    - error
+
+  'no-proto':
+    - error
+
+  'no-restricted-properties':
+    - error
+
+  'no-return-await':
+    - warn
+
+  'no-unused-expressions':
+    - error
+
+  'no-useless-call':
+    - error
+
+  'no-var':
+    - error
+
+  'object-curly-spacing':
+    - error
+    - always
+
+  'prefer-const':
+    - error
+
+  'prefer-template':
+    - error
+
+  'template-curly-spacing':
+    - error
+
+  # Disabled rules
+  '@typescript-eslint/explicit-function-return-type': off
+  '@typescript-eslint/interface-name-prefix': off
+  '@typescript-eslint/no-explicit-any': off
+  '@typescript-eslint/no-non-null-assertion': off
+  '@typescript-eslint/no-use-before-define': off
+  '@typescript-eslint/unbound-method': off
+  'no-case-declarations': off
+  'require-atomic-updates': off