use hashset instead of F# sets

Author: forki

src/Fable.React/Fable.Helpers.ReactServer.fs

@@ -9,9 +9,9 @@ open Fable.Helpers.React
 open Fable.Helpers.React.Props
 
 // Adapted from https://github.com/emotion-js/emotion/blob/182e34bab2b2028c96d513b67ed86faee1b642b2/packages/emotion-utils/src/index.js#L13
-let private unitlessCssProps = set [ "animation-iteration-count"; "border-image-outset"; "border-image-slice"; "border-image-width"; "box-flex"; "box-flex-group"; "box-ordinal-group"; "column-count"; "columns"; "flex"; "flex-grow"; "flex-positive"; "flex-shrink"; "flex-negative"; "flex-order"; "grid-row"; "grid-row-end"; "grid-row-span"; "grid-row-start"; "grid-column"; "grid-column-end"; "grid-column-span"; "grid-column-start"; "font-weight"; "line-height"; "opacity"; "order"; "orphans"; "tab-size"; "widows"; "z-index"; "zoom"; "-webkit-line-clamp"; "fill-opacity"; "flood-opacity"; "stop-opacity"; "stroke-dasharray"; "stroke-dashoffset"; "stroke-miterlimit"; "stroke-opacity"; "stroke-width" ]
+let private unitlessCssProps = System.Collections.Generic.HashSet<_>([ "animation-iteration-count"; "border-image-outset"; "border-image-slice"; "border-image-width"; "box-flex"; "box-flex-group"; "box-ordinal-group"; "column-count"; "columns"; "flex"; "flex-grow"; "flex-positive"; "flex-shrink"; "flex-negative"; "flex-order"; "grid-row"; "grid-row-end"; "grid-row-span"; "grid-row-start"; "grid-column"; "grid-column-end"; "grid-column-span"; "grid-column-start"; "font-weight"; "line-height"; "opacity"; "order"; "orphans"; "tab-size"; "widows"; "z-index"; "zoom"; "-webkit-line-clamp"; "fill-opacity"; "flood-opacity"; "stop-opacity"; "stroke-dasharray"; "stroke-dashoffset"; "stroke-miterlimit"; "stroke-opacity"; "stroke-width" ])
 
-let private voidTags = set ["area"; "base"; "br"; "col"; "embed"; "hr"; "img"; "input"; "keygen"; "link"; "menuitem"; "meta"; "param"; "source"; "track"; "wbr"]
+let private voidTags = System.Collections.Generic.HashSet<_>(["area"; "base"; "br"; "col"; "embed"; "hr"; "img"; "input"; "keygen"; "link"; "menuitem"; "meta"; "param"; "source"; "track"; "wbr"])
 
 // Adapted from https://github.com/facebook/react/blob/37e4329bc81def4695211d6e3795a654ef4d84f5/packages/react-dom/src/server/escapeTextForBrowser.js#L49
 let escapeHtml (str: string) =
@@ -36,9 +36,9 @@ let escapeHtml (str: string) =
   escaped.ToString()
 
 let inline private addUnit (key: string) (value: string) =
-  if unitlessCssProps |> Set.contains key |> not
-  then value + "px"
-  else value
+  if unitlessCssProps.Contains key 
+  then vaule
+  else value + "px"
 
 let private cssProp (key: string) (value: obj) =
   let value =
@@ -743,7 +743,7 @@ let renderToString (htmlNode: ReactElement): string =
         | Some c -> c
         | None -> (renderList (children |> Seq.map castHTMLNode))
       let attrs = if attrs = "" then attrs else " " + attrs
-      if voidTags |> Set.contains tag
+      if voidTags.Contains tag
       then "<" + tag + attrs + "/>"
       else "<" + tag + attrs + ">" + child + "</" + tag + ">"
     | HTMLNode.List nodes -> renderList (nodes |> Seq.cast)