normalize file names

book/source/index.md

@@ -12,23 +12,23 @@ SPDX-License-Identifier: CC-BY-SA-4.0
 :maxdepth: 2
 :glob:
 
-01-intro.md
-02-highlevel.md
-03-cryptography.md
-04-certificates.md
-05-private.md
-06-signatures.md
-07-signing_data.md
-08-signing_components.md
-09-verification.md
-10-encryption.md
-11-decryption.md
-12-compression.md
-13-armor.md
-14-pitfalls.md
-15-policy.md
-16-versions.md
-17-migration.md
+about.md
+openpgp.md
+cryptography.md
+certificates.md
+private.md
+signatures.md
+signing_data.md
+signing_components.md
+verification.md
+encryption.md
+decryption.md
+compression.md
+armor.md
+pitfalls.md
+policy.md
+versions.md
+migration.md
 
 adv/certificates.md
 adv/private_keys.md
@@ -41,8 +41,8 @@ zoom/private_keys.md
 zoom/signatures.md
 zoom/encyption.md
 
-23-glossary.md
-24-acknowledgements.md
+glossary.md
+acknowledgements.md
 
-a-artifacts.md
+artifacts.md
 ```