Move learning documentation from itwinjs-core repo (backport #880)

Cherry-pick of 5995ba38b3c053d8d2551a7ef460e33b0e0fc466 has failed:

On branch mergify/bp/release/4.14.x/pr-880
Your branch is up to date with 'origin/release/4.14.x'.

You are currently cherry-picking commit 5995ba38b.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
    new file:   common/changes/@itwin/appui-react/add-learning-docs-from-core_2024-06-17-20-40.json
    new file:   common/changes/@itwin/components-react/add-learning-docs-from-core_2024-06-17-20-40.json
    new file:   common/changes/@itwin/core-react/add-learning-docs-from-core_2024-06-17-20-40.json
    new file:   common/changes/@itwin/imodel-components-react/add-learning-docs-from-core_2024-06-17-20-40.json
    modified:   common/config/azure-pipelines/jobs/docs-ci.yaml
    modified:   common/config/rush/pnpm-config.json
    new file:   docs/ui/UIGlossary.md
    new file:   docs/ui/appui/configure-frontstage.md
    new file:   docs/ui/appui/define-content.md
    new file:   docs/ui/appui/get-started.md
    new file:   docs/ui/appui/index.md
    new file:   docs/ui/appui/provide-ui-items.md
    new file:   docs/ui/images/AppUiDarkTheme.png
    new file:   docs/ui/images/AppUiLightTheme.png
    new file:   docs/ui/images/FloatingViewport.png
    new file:   docs/ui/images/Form.png
    new file:   docs/ui/images/MutedText.png
    new file:   docs/ui/images/StatusBar.png
    new file:   docs/ui/images/ToolSettings.png
    new file:   docs/ui/images/comparison.svg
    new file:   docs/ui/images/stage-panel-section.svg
    new file:   docs/ui/images/stage-panel.svg
    new file:   docs/ui/images/status-bar.svg
    new file:   docs/ui/images/tool-settings.svg
    new file:   docs/ui/index.md
    new file:   docs/ui/leftNav.md
    modified:   ui/appui-react/src/appui-react.ts
    modified:   ui/components-react/src/components-react.ts
    modified:   ui/core-react/src/core-react.ts
    modified:   ui/imodel-components-react/src/imodel-components-react.ts

Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   common/config/rush/pnpm-lock.yaml

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

iTwin / appui

Move learning documentation from itwinjs-core repo (backport #880) #881