convert .less files to .css and remove dependency

res/less/song.less

@@ -1,125 +0,0 @@
-@import "colors.less";
-
-table.chordedline {
-    border-spacing: 0px;
-    display: inline-block;
-}
-
-.chordedline td {
-    padding: 0px;
-}
-
-.chord {
-    font-style: italic;
-    color: @chord-color;
-    @media (prefers-color-scheme: dark) {
-        color: @chord-color-dark;
-    }
-}
-
-.song div {
-    margin: 0.5em 0;
-}
-
-div.chorus, p.chorus {
-    font-weight: bold;
-    border-left: @text 2px solid;
-    @media (prefers-color-scheme: dark) {
-        border-left: @text-dark 2px solid;
-    }
-    padding-left: 0.5em;
-    div {
-        padding-left: 0.5em;
-    }
-    table {
-        margin-left: 0;
-        padding-left: 0;
-        padding-right: 0;
-    }
-}
-
-.rrep {
-    background-image: url(repeat-sign.svg);
-    display: inline-block;
-    width: 1em;
-    height: 2em;
-    @media (prefers-color-scheme: dark) {
-        /* Black to white filter for svgs */
-        filter: invert(100%);
-    }
-}
-
-.lrep {
-    -moz-transform: scaleX(-1);
-    -o-transform: scaleX(-1);
-    -webkit-transform: scaleX(-1);
-    transform: scaleX(-1);
-    filter: FlipV;
-    -ms-filter: "FlipV";
-    .rrep();
-}
-
-.rep {
-    font-style: italic;
-}
-
-.echo {
-    font-style: italic;
-}
-
-button,
-select,
-input[type="button"] {
-    min-width: 2em;
-    min-height: 2em;
-    padding: .4em;
-    border-style: none;
-    border-radius: @border-radius;
-    color: @text;
-    background-color: @secondary;
-    @media (prefers-color-scheme: dark) {
-        color: @text-dark;
-        background-color: @secondary-dark;
-    }
-    &:hover,
-    &.pair-sub:hover ~ &.pair-sup {
-        background-color: @secondary-hover;
-        transition-duration: @transition;
-        @media (prefers-color-scheme: dark) {
-            background-color: @secondary-hover-dark;
-        }
-    }
-}
-
-select.transposeSelect {
-    -webkit-appearance: none;
-    -moz-appearance: none;
-    font-weight: bold;
-    color: black;
-    @media (prefers-color-scheme: dark) {
-        color: @text-dark;
-    }
-}
-
-.flex-reverse {
-  display: inline-flex;
-  flex-direction: row-reverse;
-}
-
-.buttonpair.flex-reverse button.right,
-.buttonpair.flex-reverse button.left {
-    border: 1px solid @secondary-hover;
-    @media (prefers-color-scheme: dark) {
-        border-color: @secondary-hover-dark;
-    }
-}
-
-.buttonpair.flex-reverse button.right {
-  border-radius: 0px 10px 10px 0px;
-  border-width: 0 0 0 2px;
-}
-
-.buttonpair.flex-reverse button.left {
-  border-radius: 10px 0px 0px 10px;
-  border-width: 0 2px 0 0;
-}