chore: add copyright headers

Make sure we obey the REUSE (https://reuse.software) specification and the
origin, copyright owner, and license of all files are clearly marked.

The whole project is under the EPL-2.0, except for trivial files where copyright
is not applicable that are marked with the CC0-1.0 license. Moreover, code
included from third parties is also available under the respective license.

chore: add CONTRIBUTORS.md

List all authors and supporting organizations in accordance with the REUSE
specification.

5 files changed, 31 insertions, 0 deletions

diff --git a/subprojects/frontend/src/language/folding.ts b/subprojects/frontend/src/language/folding.ts
index 4dabfa27..b4d4ca22 100644
--- a/subprojects/frontend/src/language/folding.ts
+++ b/subprojects/frontend/src/language/folding.ts
@@ -1,3 +1,9 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
 import type { EditorState } from '@codemirror/state';
 import type { SyntaxNode } from '@lezer/common';
 
diff --git a/subprojects/frontend/src/language/indentation.ts b/subprojects/frontend/src/language/indentation.ts
index a0f7032d..8446d7fa 100644
--- a/subprojects/frontend/src/language/indentation.ts
+++ b/subprojects/frontend/src/language/indentation.ts
@@ -1,3 +1,10 @@
+/*
+ * Copyright (C) 2018-2021 by Marijn Haverbeke <marijnh@gmail.com> and others
+ * Copyright (C) 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: MIT OR EPL-2.0
+ */
+
 import type { TreeIndentContext } from '@codemirror/language';
 
 /**
diff --git a/subprojects/frontend/src/language/problem.grammar b/subprojects/frontend/src/language/problem.grammar
index 704badab..a7b1fb0a 100644
--- a/subprojects/frontend/src/language/problem.grammar
+++ b/subprojects/frontend/src/language/problem.grammar
@@ -1,3 +1,9 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
 @detectDelim
 
 @external prop implicitCompletion from './props'
diff --git a/subprojects/frontend/src/language/problemLanguageSupport.ts b/subprojects/frontend/src/language/problemLanguageSupport.ts
index c3ae7ed9..2121e05f 100644
--- a/subprojects/frontend/src/language/problemLanguageSupport.ts
+++ b/subprojects/frontend/src/language/problemLanguageSupport.ts
@@ -1,3 +1,9 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
 import {
   foldInside,
   foldNodeProp,
diff --git a/subprojects/frontend/src/language/props.ts b/subprojects/frontend/src/language/props.ts
index 65392e75..aa67145a 100644
--- a/subprojects/frontend/src/language/props.ts
+++ b/subprojects/frontend/src/language/props.ts
@@ -1,3 +1,9 @@
+/*
+ * SPDX-FileCopyrightText: 2021-2023 The Refinery Authors <https://refinery.tools/>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+
 /* eslint-disable import/prefer-default-export -- Lezer needs non-default exports */
 
 import { NodeProp } from '@lezer/common';