Improve Markdown formatting

* use <h3> and <hr> elements to separate configuration directives
* use <code> elements to mark constants, fs paths,
  module names etc.
* fix unneeded "\_" escaping
* fix list formatting

docs/reference/blob/fs.md

@@ -7,14 +7,15 @@ storage.blob.fs {
     root <directory>
 }
 ```
+
 ```
 storage.blob.fs <directory>
 ```
 
 ## Configuration directives
 
-**Syntax:** root _path_ <br>
-**Default:** not set
+### root _path_
+Default: not set
 
 Path to the FS directory. Must be readable and writable by the server process.
 If it does not exist - it will be created (parent directory should be writable

docs/reference/blob/s3.md

@@ -18,6 +18,7 @@ storage.blob.s3 {
 ```
 
 Example:
+
 ```
 storage.imapsql local_mailboxes {
     ...
@@ -34,53 +35,64 @@ storage.imapsql local_mailboxes {
 
 ## Configuration directives
 
-**Syntax:** endpoint _address:port\_
+### endpoint _address:port_
 
-REQUIRED.
+**Required**.
 
-Root S3 endpoint. e.g. s3.amazonaws.com
+Root S3 endpoint. e.g. `s3.amazonaws.com`
 
-**Syntax:** secure _boolean_ <br>
-**Default:** yes
+---
+
+### secure _boolean_
+Default: `yes`
 
 Whether TLS should be used.
 
-**Syntax:** access\_key _string_ <br>
-**Syntax:** secret\_key _string\_
+---
 
-REQUIRED.
+### access_key _string_<br>secret_key _string_
+
+**Required**.
 
 Static S3 credentials.
 
-**Syntax:** bucket _name\_
+---
 
-REQUIRED.
+### bucket _name_
+
+**Required**.
 
 S3 bucket name. The bucket must exist and
 be read-writable.
 
-**Syntax:** region _string_ <br>
-**Default:** not set
+---
 
-S3 bucket location. May be called "endpoint"
-in some manuals.
+### region _string_
+Default: not set
 
-**Syntax:** object\_prefix _string_ <br>
-**Default:** empty string
+S3 bucket location. May be called "endpoint" in some manuals.
+
+---
+
+### object_prefix _string_
+Default: empty string
 
 String to add to all keys stored by maddy.
 
 Can be useful when S3 is used as a file system.
 
-**Syntax:** creds _string_ <br>
-**Default:** access_key
+---
+
+### creds `access_key` | `file_minio` | `file_aws` | `iam`
+Default: `access_key`
 
 Credentials to use for accessing the S3 Bucket.
 
 Credential Types:
- - access_key: use AWS access key and secret access key 
- - file_minio: use credentials for Minio present at ~/.mc/config.json
- - file_aws: use credentials for AWS S3 present at ~/.aws/credentials
- - iam: use AWS IAM instance profile for credentials.
+
+ - `access_key`: use AWS access key and secret access key 
+ - `file_minio`: use credentials for Minio present at ~/.mc/config.json
+ - `file_aws`: use credentials for AWS S3 present at ~/.aws/credentials
+ - `iam`: use AWS IAM instance profile for credentials.
 
 By default, access_key is used with the access key and secret access key present in the config.