Incorrect closing sourcepos column for code blocks #141
Description
The sourcepos attribute for code blocks reports the column number for the line before the end of the block.
Here's a quick test case:
const commonmark = require('commonmark');
const parser = new commonmark.Parser();
// Annotated with line numbers
// 1 ```
// 2 hello world
// 3 ```
const md = '```\nhello world\n```';
const node = parser.parse(md);
const walker = node.walker();
while ((event = walker.next())) {
const {node} = event;
if (node.type === 'code_block') {
console.log(node.sourcepos);
}
}I'd expect to see [[1, 1], [3, 3]] - the backticks start at L1C1 and end at L3C3. Instead, I see [[1, 1], [3, 11]], where the closing column number (11) is the length of the hello world line before the closing backticks.