161 main menu revisions

[benlk]

Changes

This pull request makes the following changes:

• Fixes sticky appearance on browsers greater than 768px by setting position:sticky above that breakpoint. Resolves https://github.com/INN/umbrella-sfpublicpress/issues/162#issuecomment-689642320 for modern browsers, not including IE11. Included in this PR as a quick fix.
• Increases the touch target size for the .caret dropdown triggers to 44px square for all device sizes, matching Apple's Human interface Guidelines document
  • as a result, line-height on the menu drawer increases to 44px to prevent touch targets overlapping
• Fixes navigation.js elements that were predicated on an element with the .nav-shelf class being present in partials/nav-main.php, which we had earlier removed because it was messing with styling
• Removes bottom margin from nav drawer that was making it not go fullscreen
• Adds overflow rule to open nav drawer so that drop-downs which would go offscreen no longer do
• Fixes colors for dropdown carets and non-hovered links in dropdowns in the opened nav drawer
• Removes padding at top and bottom of dropdown menus in the mobile drawer

Compare these screenshots with those in #161:

Why

For #161 and #162

Testing/Questions

Features that this PR affects:

• Nav drawer

Questions that need to be answered before merging:

• [x] Is this PR targeting the correct branch in this repository?
• [ ] Should this be merged and deployed straight to staging, or do you want to review it beforehand?

Steps to test this PR:

1. On a touchscreen device, or one capable of emulating a touchscreen, try opening the drop-down menus in the main nav and in the opened mobile nav

[benlk]

Is this PR targeting the correct branch in this repository?

Looks like master is correct; there is no staging branch in this repo.