implement linear_search in Rust lang

[newvertex]

This PR implements the code for LinearSearch in Rust Lang

I have read the contributing guidelines in CONTRIBUTING.md and have ensured the following:

• [x] My code is placed in the required directory as outlined in CONTRIBUTING.md
• [ ] My code file is named according to CONTRIBUTING.md
• [ ] Variables, classes, functions etc. follow camel case as outlined in CONTRIBUTING.md
• [x] My code hasn't been implemented or claimed by someone else and I have checked the present issues and PRs for the same
• [ ] My code is well commented
• [ ] If my code is the first implementation of , I have added the link to this directory in README.md
• [x] I have not copied my code from anywhere

This PR creates/modifies the README for

I have read the contributing guidelines in CONTRIBUTING.md and have ensured the following:

• [x] Algo name (as heading)

• [ ] A small description about algo

• [ ] Time Complexity (Worst, Average, Best case)

• [ ] Space Complexity (Worst, Average, Best case)

• [ ] Logic and Pseudocode

• [x] Instructions for running code

• sides note for naming conventions I used snake_case because of Rust naming conventions

[codelixir]

Hey! Please make sure that all guidelines are being followed (for example, writing a few comments to explain your code).

Also please mention the issue number where this got assigned to you.