[Web] Show local loading spinner in sharing button

[exalate-issue-sync]

Description

User Stories

• As a user who shares a file I want to know, that the system is workign so that i'm reassured that the app is workig.

Value

Acceptance Criteria

• if a user clicks on "share" in the sharing pannel and the action takes longer than ~1 second (please try out what delay feels good), show a loading spinner before the button label
• button gets a min-width that respects the realestate of the loading spinner

Definition of ready

[ ] everybody needs to understand the value written in the user story
[ ] acceptance criteria has to be defined
[ ] all dependencies of the user story need to be identified
[ ] feature should be seen from an end user perspective
[ ] user story has to be estimated
[ ] story points need to be less then 20

Definition of done

• Functional requirements
  [ ] functionality described in the user story works
  [ ] acceptance criteria are fulfilled
• Quality
  [ ] code review happened
  [ ] CI is green
  [ ] critical code received unit tests by the developer
  [ ] automated tests passed (if automated tests are not available, this test needs to be created and passed
• Non-functional requirements
  [ ] no sonar cloud issues