Decide how to render Markdown tables

[dmalan]

Currently,

| plaintext    | `H` | `E` | `L` | `L` | `O` |
|--------------|---|---|---|---|---|
| + key        | 1 | 1 | 1 | 1 | 1 |
| = ciphertext | `I` | `F` | `M` | `M` | `P` |

renders as:

Might be cleanest to leverage https://primer.style/css/ for CSS ultimately, though ideally in a theme-independent way (i.e., no color properties).

[dmalan]

Alternatively, know what stylesheet VS Code's built-in Open Preview command uses to render Markdown? That same Markdown renders in that mode as: