Add minimum length to source embed field

I've added a minimum length to the source embed field to prevent it from
getting truncated to aggressively. Sometimes it's better to sacrifice a
newline if that means you actually get to see some information.

github_status_embed/types.py

@@ -5,6 +5,9 @@
 import typing
 
 
+MIN_EMBED_FIELD_LENGTH = 20
+
+
 class MissingActionFile(FileNotFoundError):
     """Raised when the Action file can't be located."""
 
@@ -227,6 +230,7 @@ def shortened_source(self, length: int, owner: typing.Optional[str] = None) -> s
             pr_source = pr_source.removeprefix(f"{owner}:")
 
         # Truncate the `pr_source` if it's longer than the specified length
+        length = length if length >= MIN_EMBED_FIELD_LENGTH else MIN_EMBED_FIELD_LENGTH
         if len(pr_source) > length:
             stop = length - 3
             pr_source = f"{pr_source[:stop]}..."