Made the cell line color a little darker, in coordination with
@dvchristianbors , @thinkh and @dg-datavisyn, so that it has a better
contrast and the font color can be white instead of black in Ordino.
This is how this would look like in Ordino:

![image](https://github.com/datavisyn/visyn_core/assets/57343176/0c5a332e-76aa-4d12-b591-0b45799ad34b)

### Summary of changes

- Updated the gene icons as the old one looks like some sweets
- Updated the chemical structure icon

### Screenshots
Gene icon:

![image](https://github.com/datavisyn/visyn_core/assets/57343176/a15c60f8-439e-4701-b6d9-b9a8bfd6b84e)


Chemical structure icon:

![image](https://github.com/datavisyn/visyn_core/assets/57343176/4c6a6f03-d1de-4c96-8199-18f69e8f51fe)


### Additional notes for the reviewer(s)

-  
Thanks for creating this pull request 🤗

* add css support for custom icons

* add support for entity icons

* export function to inject css for custom icons

* fix viewbox for icons and center them

* add export for icon utils

* remove inject from main app

* remove icons from main app

* remove css class injection

use app shell instead of body

…nking (#262)

* add possibility to define new score column position

* use options object parameter

* make options optional

* fix error

* deps: upgrade backend deps to latest versions

* remove flask dbmigration router

* migrate XlsxUtils to fastAPI

* linting

* fix routes

* routing fix

* migrate idtype_api to fastAPI

* refactor mainapp

* exclude health enpoint from schema

* small refactor

* fix detail_from_exception

* type ignore

* allow empty cell content

* xlsx api fixes and backend tests

* ensure all routes to have api prefix

* Add back deprecated endpoints for smooth migration

---------

Co-authored-by: Michael Puehringer <[email protected]>
Co-authored-by: Michael Pühringer <[email protected]>

refactor: update labels of filter buttons

Co-authored-by: Michael Pühringer <[email protected]>
Co-authored-by: Holger Stitz <[email protected]>

* fix violin plot selection

* partial fix vis stories

* move null value filtering to trace creation function

* disable zoom for violin plot

* small refactor

* pin storybook/node-logger

* remove resolution

* small useEffect dependency array fix

* replace null values in categorical columns with missing

* add scrollarea to multiselect

---------

Co-authored-by: Holger Stitz <[email protected]>