Workaround missing navbar @768px for dspace and custom templates

[hpwBLN]

Attribution: Donated by The Library Code

Description

Workaround: missing navbar @768px in dspace and custom templates

Instructions for Reviewers

If the screen is 768px wide, the navbar is not showing.

The treatment of the bootstrap breakpoints in DSpace is inconsistent.

md is defined as 768px <= md < 992px.

The statement

@media screen and (max-width: map-get($grid-breakpoints, md)) {}

which is in some instances used at the moment for referencing break intervals BELOW md, includes the lower md border which should be excluded.

The sass mixin
@include media-breakpoint-down($name, $grid-breakpoints) {}

or function
breakpoint-max($name, $grid-breakpoints)

which are meant to be used in this case, for some unknown reason don't seem to work atm, so the usage of

@media screen and (max-width: map-get($grid-breakpoints, md)-0.02) {}

is a solution for the moment, but this is only a workaround.
The usage of "-0.02" instead of e.g. "-0.01" is a workaround for a rounding error in Safari.

See also:
https://getbootstrap.com/docs/4.6/layout/overview/

Checklist

This checklist provides a reminder of what we are going to look for when reviewing your PR. You need not complete this checklist prior to creating your PR (draft PRs are always welcome). If you are unsure about an item in the checklist, don't hesitate to ask. We're here to help!

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes TSLint validation using yarn run lint
• My PR doesn't introduce circular dependencies
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• If my PR includes new, third-party dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.

[tdonohue]

@artlowel : Would you or someone on your team have a chance to glance at this small PR this week? It might be worth considering for 7.4, if it's non-controversial

[artlowel]

Thanks @hpwBLN!

[hpwBLN]

@artlowel, my pleasure. Thank you for reviewing.