remove dafault margin for html elements

[sudhegan]

there are default margins for html elements which are meant for programmers to avoid accessibility issues, but as we are using it in visual design, it is unnecessary and it makes many variation between design view and preview or published web view

eg: body element and p element has default margin of 8px

for reference see the follows
https://stackoverflow.com/questions/34550467/why-is-there-a-default-margin-on-the-body-element

https://t.me/frappebuilder/1/1163