Fixed mobile draw menu position when scrolled

[Charlsteezy]

PR Summary:

Fixed the bug on mobile when opening the menu draw whilst scrolled down the page. The menu now opens in the correct location rather than at the top of the page.

Why are these changes introduced?

Fixes #0.

Bug causing the draw menu to open at the top of the page on mobile when scrolled.

What approach did you take?

CSS only, simple.

Other considerations

Decision log

#	Decision	Alternatives	Rationale	Downsides
1

Visual impact on existing themes

Testing steps/scenarios

• Step 1

Demo links

• Store
• Editor

Checklist

• Added PR summary for release notes
• Requested review from UX (Only for changes that are affecting the experience or perceivable visual details)
• Created a ticket for the help.shopify.com documentation team about updates to theme settings. (Internal-only task)
• Followed theme code principles
• Linted with Theme Check
• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility

[Charlsteezy]

Filled out CLA, but put my primary email instead of the requested. :(