Adjust theme colors (#427)

* Set background color of items to transparent

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Added `superlightblue`

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Added theme to preview

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Adjusted light theme colors

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

* Got rid of unused functions

Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>

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Signed-off-by: Arnau Mora Gras <arnyminerz@proton.me>