Add testing Organice's testing files.

.gitmodules

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+[submodule "extra-tests/organice"]
+	path = extra-tests/organice
+	url = https://github.com/200ok-ch/organice.git

extra-tests/check_all.sh

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+#!/bin/sh
+
+set -eu
+
+# Get to the script's directory
+cd "`dirname $0`"
+
+# Update the extra submodules
+git submodule update --init --recursive .
+
+# Run all checks
+python3 org_dom_check.py .

extra-tests/org_dom_check.py

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+#!/usr/bin/env python3
+
+import os
+import sys
+
+import org_dom
+
+top = sys.argv[1]
+count = 0
+
+for root, dirs, files in os.walk(top):
+    for name in files:
+        if ".org" not in name:
+            continue
+
+        path = os.path.join(root, name)
+        count += 1
+        try:
+            org_dom.load(open(path), extra_cautious=True)
+        except Exception as err:
+            import traceback
+
+            traceback.print_exc()
+            print(f"== On {path}")
+            sys.exit(1)
+
+print("[OK] Check passed on {} files".format(count))

extra-tests/organice

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+Subproject commit 3c142203a6617253a1008e368af6971fc6f936a1