DOC/MINOR: improve descriptions for spell check scope options

Update the comments in `.aspell.yml` and `aspell/config_template.go` to provide a clearer, list-formatted description of the available `mode` options (`disabled`, `subject`, `commit`, `all`). This makes the configuration template easier to read and understand.

Author: oktalz

.aspell.yml

@@ -1,5 +1,8 @@
-## Spell check scope: disabled (off), subject (first line only),
-## commit (full commit message), all (commit + file content)
+## Spell check scope (default: subject)
+##   disabled - spell checking is off
+##   subject  - only check commit message subject (first line)
+##   commit   - check entire commit message (subject + body)
+##   all      - check commit message + all file content
 # mode: disabled | subject | commit | all
 mode: all
 

aspell/config_template.go

@@ -6,8 +6,11 @@ import (
 )
 
 // configTemplate is the full .aspell.yml with all options commented out and documented.
-const configTemplate = `## Spell check scope: disabled (off), subject (first line only),
-## commit (full commit message), all (commit + file content, default: subject)
+const configTemplate = `## Spell check scope (default: subject)
+##   disabled - spell checking is off
+##   subject  - only check commit message subject (first line)
+##   commit   - check entire commit message (subject + body)
+##   all      - check commit message + all file content
 # mode: disabled | subject | commit | all
 
 ## Minimum word length to spell-check (words shorter than this are skipped, default: 3)