feat: copy issue key to clipboard

[yvesjans]

I often have to copy the Jira issue key to the clipboard (create new branch, commit message, ...) This PR adds this functionality

[mk-5]

@yvesjans pls check Tests pipeline. (Goreleaser check will fail, don't worry about it)

2023/10/31 08:13:51 No clipboard utilities available. Please install xsel, xclip, wl-clipboard or Termux:API add-on for termux-clipboard-get/set.
FAIL    github.com/mk-5/fjira/internal/app  0.825s

[codecov[bot]]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (776349a) 79.22% compared to head (d2bb5c0) 79.00%. Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #88 +/- ## ========================================== - Coverage 79.22% 79.00% -0.22% ========================================== Files 65 67 +2 Lines 3181 3205 +24 ========================================== + Hits 2520 2532 +12 - Misses 514 525 +11 - Partials 147 148 +1 ``` | [Files](https://app.codecov.io/gh/mk-5/fjira/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5) | Coverage Δ | | |---|---|---| | [internal/ui/navigation.go](https://app.codecov.io/gh/mk-5/fjira/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5#diff-aW50ZXJuYWwvdWkvbmF2aWdhdGlvbi5nbw==) | `93.91% <ø> (ø)` | | | [internal/app/copy\_issue.go](https://app.codecov.io/gh/mk-5/fjira/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5#diff-aW50ZXJuYWwvYXBwL2NvcHlfaXNzdWUuZ28=) | `40.00% <40.00%> (ø)` | | | [internal/issues/copy.go](https://app.codecov.io/gh/mk-5/fjira/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5#diff-aW50ZXJuYWwvaXNzdWVzL2NvcHkuZ28=) | `0.00% <0.00%> (ø)` | | | [internal/issues/issue.go](https://app.codecov.io/gh/mk-5/fjira/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5#diff-aW50ZXJuYWwvaXNzdWVzL2lzc3VlLmdv) | `82.73% <0.00%> (-2.46%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/mk-5/fjira/pull/88/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Mk5)

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