Support single line liquid tags

[sebastienros]

[DO NOT MERGE]

This is just to track the feature which I find useful, to be able to used inlined liquid tags instead of requiring a new line before each tag.

Right now Liquid 5.1.0 doesn't support this feature.

{% liquid if name == 'tobi' 
    echo 'hello tobi'
    endif %}

Could then be written

{% liquid if name == 'tobi' echo 'hello tobi' endif %}

[sebastienros]

Shopify/liquid#1493