border styles for grid, highlight full-hour horizontal lines, fix #119

[jancborchardt]

Fix #119, please review @moy @tcitworld @nextcloud/calendar :)

Before:

After (all full-hour grid lines are darker #eee, just like the row lines in Files, user management and elsewhere):

[mention-bot]

@jancborchardt, thanks for your PR! By analyzing the history of the files in this pull request, we identified @raghunayyar, @tcitworld and @georgehrke to be potential reviewers.

[skjnldsv]

👍 okay!

[georgehrke]

👍

[coveralls]

Coverage remained the same at 42.891% when pulling 5b8a7df on grid-lines into feec09b on master.

[moy]

Much better after than before indeed IMHO. It's still rather light: for example, I'm now seeing this from my laptop's screen which has a TN panel (=> gets different contrast depending on the viewing angle). Contrast is perfect when viewed with the right angle, but the grid still disappears quickly when looking at the screen from above.

IOW, If that was just me I'd use a slightly darker color, but I'm OK with the proposal too.

Thanks!