Add comprehensive Jest test suite for MapTyper class

Co-authored-by: yuletide <58695+yuletide@users.noreply.github.com>

Author: Copilot

.gitignore

@@ -1,3 +1,5 @@
 .parcel-cache
 dist
-.env
+.env
+node_modules
+coverage

babel.config.js

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+module.exports = {
+  presets: [['@babel/preset-env', { targets: { node: 'current' } }]],
+};

jest.config.js

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+module.exports = {
+  testEnvironment: 'jsdom',
+  transform: {
+    '^.+\\.js$': 'babel-jest',
+  },
+  moduleFileExtensions: ['js'],
+  testMatch: ['**/__tests__/**/*.js', '**/?(*.)+(spec|test).js'],
+  collectCoverageFrom: ['src/**/*.js', '!src/app.js'],
+  coveragePathIgnorePatterns: ['/node_modules/'],
+};