process: Author ↦ Authors

```
sed -z -i 's/Author: /Authors: /' bip-0*.md
sed -z -i 's/Author: /Authors: /' bip-0*.mediawiki
```

Also align correctly in case of multiple authors.

bip-0374.mediawiki

@@ -2,9 +2,9 @@
   BIP: 374
   Layer: Applications
   Title: Discrete Log Equality Proofs
-  Author: Andrew Toth <andrewstoth@gmail.com>
-          Ruben Somsen <rsomsen@gmail.com>
-          Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
+  Authors: Andrew Toth <andrewstoth@gmail.com>
+           Ruben Somsen <rsomsen@gmail.com>
+           Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
   Status: Draft
   Type: Specification
   Created: 2024-12-26