[TASK] Update base.html to support pageTitle

[pxamike]

Fixes "Nimbly page template"-title on 404, 500 and search result system pages.

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PR Type

What kind of change does this PR introduce?

• [FEATURE] - A new feature
• [BUGFIX] - A bug fix
• [TASK] - Any task, which is not a new feature or bugfix
• [TEST] - Adding missing tests
• [DOC] - Documentation only changes
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Breaking change

Does this PR introduce a breaking change?

• Yes
• No

Issue references

Issue Number: #...

Description

Perhaps relevant on theme/templates/layouts/blank.html too?