Fix missing newlines in src/items-to-csv.xslt.

The GitHub Action`.github/workflows/pages-deploy.yaml` is set to use
`ubuntu-latest`, which was Ubuntu 18.04 for the initial release and
Ubuntu 20.04 as of the last commit 954cc5d (90ff811). For the most recent
build cd7ac80 (bba081f), `ubuntu-latest` points to Ubuntu 22.04.

tdewolff/minify@200330f7 (first in v2.6.0) made it so that `minify`
automatically expands any character entities in the input XML.
Unfortunately, due to XML attribute whitespace normalization, a newline
in an attribute is processed as a space. Ubuntu 20.04 contains
`minify` v2.5.2 while Ubuntu 22.04 contains `minify` v2.9.22, so the
recent upgrade caused the issue to appear.

To fix this, we'll use `<xsl:text>` elements instead of a `$variable`
since elements use less aggressive whitespace normalization than
attributes. We still need to use a character entity plus a trailing
space though to prevent the minifier + normalization combo from deleting
the newline.

Thanks to @WoodlandSkipper for tracking down the issue in the comments
of #5.

src/items-to-csv.xslt

@@ -3,21 +3,21 @@
     <!-- Stardew Valley Item Finder
      https://gucci-on-fleek.github.io/Stardew-Valley-Item-Finder/
      SPDX-License-Identifier: MPL-2.0+
-     SPDX-FileCopyrightText: 2022 Max Chernoff
+     SPDX-FileCopyrightText: 2024 Max Chernoff
 -->
     <xsl:output method="text" encoding="utf-8" />
 
     <xsl:variable name="col_sep" select="','" />
     <xsl:variable name="quote" select="''" />
-    <xsl:variable name="row_sep" select="'&#xA;'" />
 
     <xsl:template match="/items">
         <xsl:value-of select="concat($quote, 'Item Name', $quote, $col_sep)" />
         <xsl:value-of select="concat($quote, 'Quality', $quote, $col_sep)" />
         <xsl:value-of select="concat($quote, 'Price', $quote, $col_sep)" />
         <xsl:value-of select="concat($quote, 'Count', $quote, $col_sep)" />
         <xsl:value-of select="concat($quote, 'Stored in', $quote, $col_sep)" />
-        <xsl:value-of select="concat($quote, 'Stack Price', $quote, $row_sep)" />
+        <xsl:value-of select="concat($quote, 'Stack Price', $quote)" />
+        <xsl:text>&#xA; </xsl:text>
 
         <xsl:for-each select="item">
             <xsl:sort select="actual_price * count" data-type="number" order="descending" />
@@ -48,7 +48,7 @@
                 </xsl:otherwise>
             </xsl:choose>
             <xsl:value-of select="concat($quote, actual_price * count, $quote)" />
-            <xsl:value-of select="$row_sep" />
+            <xsl:text>&#xA; </xsl:text>
         </xsl:for-each>
     </xsl:template>