Clarify project initialization commands in README

[jayenashar]

This pull request updates the project setup instructions in the README.md to clarify the initialization process for new and existing projects.

• Documentation update:
  • Updated the setup steps to recommend codev init for new projects and added codev adopt for existing projects in the README.md instructions.

[waleedkadous]

We can give clearer instructions here:

codev init <dir_name>

or

cd <dir>
codev adopt

[jayenashar]

codev init prompts me for the directory to create

if you're willing to change the cli, codev init [dir-name] can work for all use cases:

• no dir-name specified - prompts user (as now)
• dir-name specified and does not exist - creates folder (as now)
• dir-name specified, exists, is empty - sets up folder
• dir-name specified, exists, is not empty - sets up folder (change from now which refuses. adopt can be an alias for init .)

P.S. imho dir-name should be in square brackets to indicate optionality.