Add room header buttons to access sidepanes

src/icons/thin/go-back-to-main-pane.svg

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+<svg enable-background="new 0 0 512 512" height="512" viewBox="0 0 512 512" width="512" xmlns="http://www.w3.org/2000/svg">
+    <path d="m157.11671 264.09364 163.98439 163.9844c2.34598 2.34598 5.04388 3.51897 8.09365 3.51897 3.04979 0 5.74768-1.17299 8.09364-3.51897l17.59491-17.59489c2.34598-2.34599 3.51897-5.04386 3.51897-8.09365 0-3.04981-1.17299-5.74766-3.51897-8.09366l-138.29586-138.29584 138.29586-138.29584c2.34598-2.34599 3.51897-5.04388 3.51897-8.09366s-1.17299-5.74766-3.51897-8.09364l-17.59491-17.594899c-2.34596-2.345973-5.04385-3.518979-8.09364-3.518979-3.04977 0-5.74767 1.173006-8.09365 3.518979l-163.98439 163.984399c-2.34598 2.34598-3.51898 5.04385-3.51898 8.09364 0 3.0498 1.173 5.74767 3.51898 8.09364z" stroke-width=".351898"/>
+</svg>

src/icons/thin/go-to-room-pane.svg

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+<svg enable-background="new 0 0 512 512" height="512" viewBox="0 0 512 512" width="512" xmlns="http://www.w3.org/2000/svg">
+    <path d="m354.88329 264.09364-163.98439 163.9844c-2.34598 2.34598-5.04388 3.51897-8.09365 3.51897-3.04979 0-5.74768-1.17299-8.09364-3.51897l-17.59491-17.59489c-2.34598-2.34599-3.51897-5.04386-3.51897-8.09365 0-3.04981 1.17299-5.74766 3.51897-8.09366l138.29586-138.29584-138.29586-138.29584c-2.34598-2.34599-3.51897-5.04388-3.51897-8.09366s1.17299-5.74766 3.51897-8.09364l17.59491-17.594899c2.34596-2.345973 5.04385-3.518979 8.09364-3.518979 3.04977 0 5.74767 1.173006 8.09365 3.518979l163.98439 163.984399c2.34598 2.34598 3.51898 5.04385 3.51898 8.09364 0 3.0498-1.173 5.74767-3.51898 8.09364z" stroke-width=".351898"/>
+</svg>