Add styling that improves readability

- article content with a max-width, + index page
- code sections are bordered, indented and padded
- figure captions are centered along with the images
- h2 margin is only removed in non-articles; the post index page
- main with extra space at the bottom to allow scolling past content

client/public/assets/styling/general.css

@@ -17,6 +17,28 @@ nav {
   border-bottom-right-radius: 5px;
 }
 
+main {
+  padding-bottom: 12em;
+}
+
+article {
+  max-width: 1000px;
+  margin: auto;
+}
+
+pre {
+  padding: 1em;
+  padding-left: 2em;
+  border: solid;
+  border-radius: 1em;
+  border-width: 1px;
+  border-color: var(--text-color);
+}
+
+.figure > p {
+  text-align: center;
+}
+
 .question {
   font-style: italic;
 }
@@ -27,6 +49,9 @@ h1 {
 
 h2 {
   font-size: 1.25em;
+}
+
+main > h2 {
   margin: auto 0;
 }