Extend .gitattributes: source files to eol=lf

csharpier check fails with 'different line endings than formatting would
result in' when .cs files are CRLF. Linux dev box and Gitea Actions
runners both work with LF natively. Extend the LF-override to .cs,
.csproj, .sln, .yml, .yaml, .json, .md.

Asriel's original CRLF default still applies to file types not listed,
to keep the diff against upstream minimal.

.gitattributes

@@ -10,4 +10,16 @@
 .githooks/*    text eol=lf
 scripts/*      text eol=lf
 
+# csharpier check fails with "different line endings than formatting would
+# result in" when .cs files are CRLF. The Gitea Actions runners are Linux
+# and the local dev box is Linux too, so force LF for the entire source
+# tree and the supporting text manifests.
+*.cs           text eol=lf
+*.csproj       text eol=lf
+*.sln          text eol=lf
+*.yml          text eol=lf
+*.yaml         text eol=lf
+*.json         text eol=lf
+*.md           text eol=lf
+
 *.png binary