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-0046.mediawiki

@@ -2,8 +2,8 @@
   BIP: 46
   Layer: Applications
   Title: Address Scheme for Timelocked Fidelity Bonds
-  Author: Chris Belcher <belcher@riseup.net>
-          Thebora Kompanioni <theborakompanioni+bip46@gmail.com>
+  Authors: Chris Belcher <belcher@riseup.net>
+           Thebora Kompanioni <theborakompanioni+bip46@gmail.com>
   Status: Draft
   Type: Specification
   Created: 2022-04-01