add 'align' parameter to figure shortcode

Parameter values:
  - unset or 'default': align according to language direction
  - 'left': align image and captions to left of page
  - 'right': align image and captions to right of page
  - 'center': align image and captions to center of page

assets/css/post-single.css

@@ -242,6 +242,27 @@
     margin: auto
 }
 
+.post-content figure.align-center {
+	display: flex;
+	flex-direction: column;
+	align-items: center;
+	text-align: center;
+}
+
+.post-content figure.align-left {
+	display: flex;
+	flex-direction: column;
+	align-items: flex-start;
+	text-align: left;
+}
+
+.post-content figure.align-right {
+	display: flex;
+	flex-direction: column;
+	align-items: flex-end;
+	text-align: right;
+}
+
 .post-content figure > figcaption {
     color: var(--primary);
     font-size: 16px;

layouts/shortcodes/figure.html

@@ -1,4 +1,7 @@
-<figure{{ with .Get "class" }} class="{{ . }}"{{ end }}>
+<figure{{ if or (.Get "class") (.Get "align") }} class="
+           {{- with .Get "align" }}align-{{ . }} {{ end }}
+           {{- with .Get "class" }}{{ . }}{{ end }}"
+{{- end -}}>
     {{- if .Get "link" -}}
         <a href="{{ .Get "link" }}"{{ with .Get "target" }} target="{{ . }}"{{ end }}{{ with .Get "rel" }} rel="{{ . }}"{{ end }}>
     {{- end }}