Configure CLI options SILE to be used as a PDF engine

MANUAL.txt

@@ -1447,8 +1447,8 @@ header when requesting a document from a URL:
 :   Use the specified engine when producing PDF output.
     Valid values are `pdflatex`, `lualatex`, `xelatex`, `latexmk`,
     `tectonic`, `wkhtmltopdf`, `weasyprint`, `pagedjs-cli`,
-    `prince`, `context`, `pdfroff`, and `typst`. If the engine is not in
-    your PATH, the full path of the engine may be specified here.
+    `prince`, `context`, `pdfroff`, `sile`, and `typst`. If the engine is not
+    in your PATH, the full path of the engine may be specified here.
     If this option is not specified, pandoc uses the following
     defaults depending on the output format specified using
     `-t/--to`:
@@ -1461,6 +1461,7 @@ header when requesting a document from a URL:
         see [print-css.rocks](https://print-css.rocks) for a good
         introduction to PDF generation from HTML/CSS)
     - `-t ms`:  `pdfroff`
+    - `-t sile`: `sile`
     - `-t typst`: `typst`
 
 `--pdf-engine-opt=`*STRING*

src/Text/Pandoc/App/CommandLineOptions.hs

@@ -222,6 +222,7 @@ engines = map ("html",) htmlEngines ++
           map ("latex",) latexEngines ++
           map ("beamer",) latexEngines ++
           [ ("ms", "pdfroff")
+          , ("sile", "sile")
           , ("typst", "typst")
           , ("context", "context")
           ]

src/Text/Pandoc/PDF.hs

@@ -92,6 +92,12 @@ makePDF program pdfargs writer opts doc =
       source <- writer opts doc
       verbosity <- getVerbosity
       liftIO $ toPdfViaTempFile verbosity program pdfargs mkOutArgs source
+    "sile" -> do
+      let mkOutArgs f = ["-o", f]
+      source <- writer opts doc
+      verbosity <- getVerbosity
+      liftIO $
+        toPdfViaTempFile verbosity program pdfargs mkOutArgs source
     "typst" -> do
       source <- writer opts doc
       verbosity <- getVerbosity