fix: normalize docs/funcs source to LF to match its embedded copy

The previous commit forced the embedded function docs to LF, but their
source of truth, docs/funcs/, still had no end-of-line rule - so a
Windows (autocrlf) checkout left it CRLF. TestFuncDocsSourceMatchesEmbedded
then compared the CRLF source against the now-LF embedded copy and failed.

Mark docs/funcs/ `text eol=lf` too, so both sides of that byte-for-byte
mirror check out LF everywhere. Blobs are already LF; no content change.

Author: amterp

.gitattributes

@@ -12,3 +12,8 @@ rts/embedded/functions.txt            linguist-generated=true text eol=lf
 rts/signatures_gen.go                 linguist-generated=true
 docs-web/docs/reference/functions.md  linguist-generated=true
 docs-web/docs/reference/errors.md     linguist-generated=true
+
+# Per-function doc source of truth, mirrored byte-for-byte into the embedded
+# copy (rts/embedded_funcs/) with a test asserting they match - so the source
+# must share the embedded copy's LF endings on every platform.
+docs/funcs/**                         text eol=lf