guide: add Configuration guide (#4379)

* guide: add Config guide

per #340

* Include basic remote storage config info and...

and/or link to
https://dvc.org/doc/user-guide/data-management/remote-storage

* Update content/docs/command-reference/config.md

Co-authored-by: Dave Berenbaum <[email protected]>

* Restyled by prettier (#4383)

Co-authored-by: Restyled.io <[email protected]>

* guide: update links to Config info. (#4380)

* guide: Update links to config sections

Previously in the cmd ref, now in a new guide

* guide: some more links related to `dvc config` instances

* guide: update links from `dvc config` (ref) to new guide

* guide: clarify about other config file locations

per #4379 (review)

* guide: refinements

per #4379 (review)
and #4379 (comment)

* Update content/docs/user-guide/project-structure/configuration.md

---------

Co-authored-by: Dave Berenbaum <[email protected]>

---------

Co-authored-by: Dave Berenbaum <[email protected]>
Co-authored-by: restyled-io[bot] <32688539+restyled-io[bot]@users.noreply.github.com>
Co-authored-by: Restyled.io <[email protected]>

content/docs/command-reference/add.md

@@ -58,7 +58,7 @@ other DVC commands), a few actions are taken under the hood:
 [remote storage]: /doc/user-guide/data-management/remote-storage
 [structure of cache directory]:
   /doc/user-guide/project-structure/internal-files#structure-of-the-cache-directory
-[`core.autostage`]: /doc/command-reference/config#core
+[`core.autostage`]: /doc/user-guide/project-structure/configuration#core
 
 Summarizing, the result is that the target data is replaced by small `.dvc`
 files that can be easily tracked with Git.

content/docs/command-reference/checkout.md

@@ -45,15 +45,18 @@ after `git checkout`. See the
 for more details.
 
 By default, this command tries not make copies of cached files in the workspace,
-using reflinks instead when supported by the file system (refer to
-[File link types](/doc/user-guide/data-management/large-dataset-optimization#file-link-types-for-the-dvc-cache)).
-The next linking strategy default value is `copy` though, so unless other file
-link types are manually configured in `cache.type` (using `dvc config`), files
-will be copied. Keep in mind that having file copies doesn't present much of a
-negative impact unless the project uses very large data (several GBs or more).
-But leveraging file links is crucial with large files, for example when checking
-out a 50Gb file by copying might take a few minutes whereas, with links,
-restoring any file size will be almost instantaneous.
+using reflinks instead when supported by the file system (refer to [File link
+types]). The next linking strategy default value is `copy` though, so unless
+other file link types are manually configured in [`cache.type`]), files will be
+copied. Keep in mind that having file copies doesn't present much of a negative
+impact unless the project uses very large data (several GBs or more). But
+leveraging file links is crucial with large files, for example when checking out
+a 50Gb file by copying might take a few minutes whereas, with links, restoring
+any file size will be almost instantaneous.
+
+[File link types]:
+  /doc/user-guide/data-management/large-dataset-optimization#file-link-types-for-the-dvc-cache
+[`cache.type`]: /doc/user-guide/project-structure/configuration#cache
 
 > When linking files takes longer than expected (10 seconds for any one file)
 > and `cache.type` is not set, a warning will be displayed reminding users about
@@ -95,7 +98,8 @@ situation. In some cases, the data can be pulled from [remote storage] using
 
 - `--relink` - ensures the file linking strategy (`reflink`, `hardlink`,
   `symlink`, or `copy`) for all data in the workspace is consistent with the
-  project's [`cache.type`](/doc/command-reference/config#cache). This is
+  project's
+  [`cache.type`](/doc/user-guide/project-structure/configuration#cache). This is
   achieved by restoring **all data files or directories** referenced in current
   DVC files (regardless of whether the files/dirs were already present).