explorer: cannot see filters in darkmode

[enekofb]

Describe the bug
explorer in darkmode has filters letters in black so cannot see them.

To Reproduce

1. Start WGE without darkmode
2. Go to explorer and open filters. you see filters and can filter
3. Switch to darkmode
4. you cannot see filters

environment you could test https://gitops.internal-dev.wego-gke.weave.works/explorer/query

Actual behaviour

I cannot filter in dark mode

Expected behaviour

I can filter in dark mode

[jpellizzari]

This is happening in a few more places. Cluster Detail:

Related to body not observing theme colors:

weave-gitops-enterprise/ui/src/App.tsx

Line 90 in 76f30e1

color: ${props => props.theme.colors.black};