Can't create nested admonitions

[lebalz]

Currently, no nested admonitions are possible.

:::info Weather
On nice days, you can enjoy swimming in the lake.

:::danger Storms
Take care of summerstorms...
:::

:::

Will result in only one admonition instead of a nested admonition.

Issue

index.js:172 stops at the first seen closing tag

// the closing tag is NOT part of the content
if (line.startsWith(config.tag)) break;