Add advisory for segmentation fault in grcov (#2191)

* Add advisory for segmentation fault in grcov

* More clear description based on the linked bug and the patch

---------

Co-authored-by: Sergey "Shnatsel" Davidoff <shnatsel@gmail.com>

Author: nyw0102

crates/grcov/RUSTSEC-0000-0000.md

@@ -0,0 +1,20 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "grcov"
+date = "2025-01-13"
+url = "https://bugzilla.mozilla.org/show_bug.cgi?id=1917475"
+categories = ["memory-corruption"]
+
+[affected]
+functions = { "grcov::covdir::get_coverage" = ["<=0.8.20"] }
+
+[versions]
+patched = [">0.8.20"]
+```
+# Out of bounds write triggered by crafted coverage data
+Function `grcov::covdir::get_coverage` uses the `unsafe` function `get_unchecked_mut`
+without validating that the index is in bounds.
+
+This results in memory corruption, and could potentially allow arbitrary code execution
+provided that an attacker can feed the tool crafted coverage data.