Update README.md

[mirnawong1]

this pr adds an intro to dbt core as well as bullets for the diff ways to deploy dbt. this stemmed from task last year: https://www.notion.so/dbtlabs/Mirna-will-review-cloud-cli-repo-per-Greg-s-request-0a372ebb66794a749350b0fbb36ee266?pvs=4

Problem

currently its not clear the ways to deploy dbt, this pr tries to clarify that a little.

Solution

Checklist

• [ x] I have read the contributing guide and understand what's expected of me
• [ ] I have run this code in development and it appears to resolve the stated issue
• [ ] This PR includes tests, or tests are not required/relevant for this PR
• [x ] This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• [ ] This PR includes type annotations for new and modified functions

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.78%. Comparing base (71a8a41) to head (45bbaf6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #10324 +/- ## ========================================== - Coverage 88.83% 88.78% -0.06% ========================================== Files 180 180 Lines 22490 22490 ========================================== - Hits 19980 19967 -13 - Misses 2510 2523 +13 ``` | [Flag](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10324/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | Coverage Δ | | |---|---|---| | [integration](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10324/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | `86.04% <ø> (-0.15%)` | :arrow_down: | | [unit](https://app.codecov.io/gh/dbt-labs/dbt-core/pull/10324/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs) | `62.19% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dbt-labs#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.