update docs css for better in-line monospace highlighting

[shahidhk]

We need to add the following CSS to docs:

code .docutils .literal {
    padding: 0.2em 0.4em;
    margin: 0;
    background-color: rgba(27,31,35,0.05);
    border-radius: 3px;
}

This gives better highlighting for in-line monospace text, wrapped in ``<text>`` blocks within rst.

before:

after: