imp:cli:html output: add a charset=UTF-8 meta header [#2301]

For general correctness of reports' HTML output.

hledger-lib/Hledger/Write/Html/Lucid.hs

@@ -25,6 +25,7 @@ type Html = Html.Html ()
 
 printHtml :: (Lines border) => [[Cell border Html]] -> Html
 printHtml table = do
+    Html.meta_ [Html.charset_ "UTF-8"]
     Html.link_ [Html.rel_ "stylesheet", Html.href_ "hledger.css"]
     Html.style_ Attr.tableStylesheet
     Html.table_ $ traverse_ formatRow table