issue: #4427; Added the Alternate text to image tags

[sathiyaIbe]

Yeah it's my first contribution I had updated the images with missing alt : alternate text to the image tag So kindly check the changed files

[welcome[bot]]

💖 Thanks for opening this pull request! 💖

Here is a list of things that will help get it across the finish line:

• Run yarn lint locally to catch formatting errors. This will fix some errors automatically, commit and push any changes.
• Run yarn test locally to catch errors. This ensures all components still behave as they should.
• Run yarn start to run the doc site locally and try a few pages, ensuring everything is in good working order.
• Include tests when adding/changing behavior.

We get a lot of pull requests on this repo, so please be patient and we will get back to you as soon as we can.

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (038b306) 99.51% compared to head (4400b7f) 99.51%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4429 +/- ## ======================================= Coverage 99.51% 99.51% ======================================= Files 186 186 Lines 3511 3511 ======================================= Hits 3494 3494 Misses 17 17 ``` | [Impacted Files](https://app.codecov.io/gh/Semantic-Org/Semantic-UI-React/pull/4429?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Semantic-Org) | Coverage Δ | | |---|---|---| | [src/modules/Embed/Embed.js](https://app.codecov.io/gh/Semantic-Org/Semantic-UI-React/pull/4429?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Semantic-Org#diff-c3JjL21vZHVsZXMvRW1iZWQvRW1iZWQuanM=) | `100.00% <ø> (ø)` | |

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