Parsing Markdown Tables

Implement parse_table(md) that turns a Markdown pipe table into a list of dicts:

| name | qty |
|------|----:|
| pen  | 3   |

• the first row is the header, the second is the separator (cells of dashes with optional colons) and must be present, otherwise raise ValueError
• leading/trailing pipes are optional; cells are stripped
• escaped pipes \| inside cells are literal |
• rows with fewer cells are padded with ""; rows with more raise ValueError
• ignore blank lines