Escape of dots in list items

[susnux]

When there are dots, following a number, as text in list items they must be escaped.
Found by an user of the nextcloud text app: nextcloud/text#2480

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E.g. consider this text:

Hello

• 1. world
• 2. world
• 3. world

which is based on this source code:

Hello
* 1\. world
* 2\. world
* 3\. world

But using the WYSIWYG editor it emits this markdown:

Hello
* 1. world
* 2. world
* 3. world

which results in:

Hello

• 1. world
• 2. world
• 3. world

See also this example:

[marijnh]

Attached patch should help.