Give release binaries file extensions

This may make it more clear to users that these are precompiled, binary
files. This is especially relevant on Windows, where the convention is
that executable files have a .exe` extension, as seen in #49.

.github/workflows/release.yml

@@ -53,7 +53,7 @@ jobs:
         with:
           upload_url: ${{ needs.create-release.outputs.upload_url }}
           asset_path: target/release/obsidian-export
-          asset_name: obsidian-export_Linux-x86_64
+          asset_name: obsidian-export_Linux-x86_64.bin
           asset_content_type: application/octet-stream
 
   build-windows:
@@ -87,7 +87,7 @@ jobs:
         with:
           upload_url: ${{ needs.create-release.outputs.upload_url }}
           asset_path: target/release/obsidian-export.exe
-          asset_name: obsidian-export_Windows-x64_64
+          asset_name: obsidian-export_Windows-x64_64.exe
           asset_content_type: application/octet-stream
 
   build-macos:
@@ -121,5 +121,5 @@ jobs:
         with:
           upload_url: ${{ needs.create-release.outputs.upload_url }}
           asset_path: target/release/obsidian-export
-          asset_name: obsidian-export_MacOS-x86_64
+          asset_name: obsidian-export_MacOS-x86_64.bin
           asset_content_type: application/octet-stream