handle patches with no offset 🫡 (#15)

Sometimes, e.g., when a one line file is added or when a file is
entirely removed, the patch's new line numbers contain only a single
number (e.g., `@@ -0,0 +1 @@` or `@@ -1,224 +1 @@`).

Previously this would panic. Instead, handle it gracefully!

remove `details` from annotation 🖍️ (#7)

Remove the `details` field from all annotations. In certain conditions,
including this field (which was filled with a marshalled JSON string)
appears to be causing a validation error in posting an initial check
creation to GitHub. In the reproduced error cases, the post body
remained valid JSON, but nonetheless removing the `details` field
resolved the validation issue.

deduplicate sarif results 🚫👯 (#5)

When a sarif result is reported multiple times (with the same file,
lines, level, and id), collapse all the reports into one annotation.

override check name 📇 (#1)

Add a flag to allow users to modify the name assigned to the check.

annotate first line by default 🆙

treat empty file as `{}` 😶

When a sarif file exists but has no contents, treat it as _valid_ but
with no findings. Semgrep outputs this when it has no findings.

handle 0 non-filtered annotations 0️⃣