Added new company I-STEM

[Ram-tyagi]

This is a modified version of, and should adhere to, the Contributing Guidelines.

• This PR contains housekeeping only (URL edits, copy changes etc) - if this is checked, delete other lines that don't apply

• You are an employee of the company mentioned and confirm all included details are correct.

• You know your alphabet - company is listed in alphabetical order in the README.md file.

• The company directly hires employees. No bootcamps / freelance sites / etc

• The company hires remote employees, or positions are available to remote workers and are clearly illustrated as such.

• A company profile is included - This is required for new additions.

• An entry has been added or edited within the readme.md file.

• Remote status has details regarding how the culture includes remote employees, how the company integrated remote workers, etc

• Region details the geographic regions in which this company employees can reside. For more details see the instructions in the example company profile.

• How to apply details the best approach for new applications, page on site where open position are listed, and any other help available for job hunters

[Ki-er]

@Ram-tyagi Please make a new PR for the other company