docs: use openair pkgdown theme

DESCRIPTION

@@ -42,6 +42,7 @@ Suggests:
     rmarkdown
 VignetteBuilder: 
     knitr
+Config/Needs/website: openair-project/openairpkgdown
 Encoding: UTF-8
 Language: en-GB
 LazyData: yes

_pkgdown.yml

@@ -1,34 +1,17 @@
 url: https://openair-project.github.io/deweather/
 template:
-  bootstrap: 5
-  bslib:
-    bootswatch: lumen
-    pkgdown-nav-height: 100px
+  package: openairpkgdown
 
 navbar:
-  title: deweather
-  structure:
-    left:  [intro, reference, news, articles, tutorials, book, casestudy]
-    right: [search, github]
-  components:
-    reference:
-      text: Functions
-      href: reference/index.html
-    news:
-      text: News
-      href: news/index.html
-    book:
-      text: Book (External)
-      href: https://bookdown.org/david_carslaw/openair/
-    casestudy:
-      text: Case Studies (External)
-      menu:
-      - text: (2019) Using meteorological normalisation to detect interventions in air quality time series
-        href: https://www.sciencedirect.com/science/article/pii/S004896971834244X
-      - text: (2012) A short-term intervention study — Impact of airport closure due to the eruption of Eyjafjallajökull on near-field air quality
-        href: https://www.sciencedirect.com/science/article/abs/pii/S1352231012001355
-      - text: (2009) Analysis of air pollution data at a mixed source location using boosted regression trees
-        href: https://www.sciencedirect.com/science/article/abs/pii/S1352231009003069
+  casestudy:
+    text: Case Studies (External)
+    menu:
+    - text: (2019) Using meteorological normalisation to detect interventions in air quality time series
+      href: https://www.sciencedirect.com/science/article/pii/S004896971834244X
+    - text: (2012) A short-term intervention study — Impact of airport closure due to the eruption of Eyjafjallajökull on near-field air quality
+      href: https://www.sciencedirect.com/science/article/abs/pii/S1352231012001355
+    - text: (2009) Analysis of air pollution data at a mixed source location using boosted regression trees
+      href: https://www.sciencedirect.com/science/article/abs/pii/S1352231009003069
 
 reference:
 - title: Data