docs(en): add selection sort

[Sunainacode]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• New algorithm
• Optimization in previous algorithms
• Code style update
• Refactor
• Documentation
• Other, please describe:

Briefly describe the changes in this PR

Added documentation for Selection Sort Algorithm
Other information:

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[ming-tsai]

Hi @Sunainacode,
Please rewrite the steps and example sections, take the Bubble Sort as an example

The example section could be like this

Given array is
**13, 44, 5, 34, 3**

Sorted array is
**3, 5, 13, 34, 44**

**First pass**

Unsorted array: [13, 44, 5, 34, 3]

Minimum in an unsorted array: 3

Sorted array: [3]

**Second pass**

Unsorted array: [13, 44, 5, 34]

Minimum in unsorted array: 5

Sorted array: [3, 5]

**Third pass**

Unsorted array: [13, 44, 34]

Minimum in an unsorted array: 13

Sorted array: [3, 5, 13]

...

[Sunainacode]

Hi @ming-tsai.
Can you please review the changes now?

[ming-tsai]

Nice work @Sunainacode

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