Docs: Add license, code of conduct, Contributing and security guidelines

[LakshmiSaiHarika]

Please review the overall draft of this doc PR.

This PR features the following:

• Added MIT License for this project.
• Added code of conduct to highlight the guidelines to follow in order to make contributions in this project.
• Added Contributing guide to explain the procedure for making contributions in this project.
• Added Security Guidelines to report a security bug.

[LakshmiSaiHarika]

Please help me with few of the questions I posted in the comments section.

[benland72]

The updates look good to me. Thank you!

[markg-github]

I added a lot of (19) comments - all minor. (It helps me stay engaged. :))

Approving and deferring to Ben for whether describing squashing, as he describes, is gating.

[DGonzalezVillal]

Some wording and content suggestions. Please also look through Mark's comments because he also found several grammar and content mistakes.

[npmccallum]

1. Content is very good!

2. Be sure to wrap all files at an 80 column boundary. Keep in mind the rule about Markdown that it should be readable from both a terminal and the web.

3. Please make sure to include the "disclaimer" that @benland72 mentioned.

4. Sometimes you write long paragraphs with no wrapping. Other times, you write with a new sentence on each line. Markdown should flow like good English text with paragraphs and spacing to make it readable.

5. There's a good Markdown style guide here: https://github.com/carwin/markdown-styleguide You might consider it as good advice. But remember, all rules have a time when they should be broken.

[LakshmiSaiHarika]

1. Content is very good!
2. Be sure to wrap all files at an 80 column boundary. Keep in mind the rule about Markdown that it should be readable from both a terminal and the web.
3. Please make sure to include the "disclaimer" that @benland72 mentioned.
4. Sometimes you write long paragraphs with no wrapping. Other times, you write with a new sentence on each line. Markdown should flow like good English text with paragraphs and spacing to make it readable.
5. There's a good Markdown style guide here: https://github.com/carwin/markdown-styleguide You might consider it as good advice. But remember, all rules have a time when they should be broken.

I organized my content into a text with paragraphs and spacing to make it more readable as per the above comments.
Please take a look

[DGonzalezVillal]

Just some proof reading things and then a comment around the mkosi reference. Is there a specific reason why we mention mkosi in the code of conduct? If not I think it makes more sense to move the mksoi reference to the contribution guide.

[DGonzalezVillal]

Suggested change

	When *adding new operating system images or modifying existing ones*, please use mkosi to build your host/guest image and verify that it boots successfully on your system before submitting a pull request. This ensures that the functionality being introduced is working as expected prior to code review.
	When *adding new operating system images or modifying existing ones*, please use [mkosi](https://github.com/systemd/mkosi) to build your host/guest image and verify that it boots successfully on your system before submitting a pull request. This ensures that the functionality being introduced is working as expected prior to code review.

I think referencing the mkosi tool makes more sense here.

[LakshmiSaiHarika]

I added mkosi hyperlink as per your suggestion.

[LakshmiSaiHarika]

Thanks for your re-review @DGonzalezVillal! I addressed your above feedback.

Harika addressed the comments, Nathaniel OOO