Add commit hook for building javascript

.githooks/pre-commit

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# This commit hook checks whether we ran `yarn build` when committed TypeScript files.
+# For GitHub actions to work, we need to check the compiled JavaScript into VCS.
+#
+# This script can yield false positives in cases where you only make stylistic changes to the TypeScript code that don't result in changes to the compiled JavaScript code.
+# It is your responsibility as a developer to then commit the changes with `git commit --no-verify` and simply skip this commit hook.
+
+TS_FILES=$(git diff --staged --name-only | grep -c '.ts')
+DIST_MODIFIED=$(git diff --staged --name-only | grep -c dist/index.js)
+
+if [ $TS_FILES -gt 0 ] && [ $DIST_MODIFIED -eq 0 ] ; then
+    echo "You modified TypeScript files but apparently did not run 'yarn build'".
+    exit 1;
+fi

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+-   Commit hook for preventing dist/index.js to be out of date after modifying Typescript files.
+
 ## [1.1.0] - 2020-02-17
 
 ### Added