Update MANUAL.txt

Author: christopherkenny

MANUAL.txt

@@ -2728,7 +2728,7 @@ Currently the following pipes are predefined:
     documents
 
 `abstract-title`
-:   title of abstract, currently used only in HTML, EPUB, and docx.
+:   title of abstract, currently used only in HTML, EPUB, docx, and Typst.
     This will be set automatically to a localized value,
     depending on `lang`, but can be manually overridden.
 
@@ -3391,6 +3391,19 @@ The `--css` option also affects the output.
 `columns`
 :    Number of columns for body text.
 
+`thanks`
+:   contents of acknowledgments footnote after document title
+
+`mathfont`, `codefont`
+:    Name of system font to use for math and code, respectively.
+
+`linestretch`
+:   adjusts line spacing, e.g. `1.25`, `1.5`
+
+`linkcolor`, `filecolor`, `citecolor`
+:   color for external links, internal links, and citation links,
+    respectively: expects a hexadecimal color code
+
 ### Variables for ms
 
 `fontfamily`