docs: update style guidelines (#2172)

Update the style guidelines.

Co-authored-by: Clément Michaud <clement.michaud34@gmail.com>

docs/contributing/style-guide.md

@@ -42,3 +42,60 @@ This includes but is not limited to the following file types:
 - Markdown (*.md)
 - JavaScript (*.js)  
 - TypeScript (*.ts, *.tsx)
+
+### Error Strings
+
+Error messages should follow the standard go format. This format can be found in the [golang code review comments](https://github.com/golang/go/wiki/CodeReviewComments#error-strings)
+however the key points are:
+
+- errors should not start with capital letters (excluding proper nouns, acronyms, or initialism)
+- errors should not end with punctuation
+- these restrictions do not apply to logging, only the error type itself
+
+### Configuration Documentation
+
+The configuration documentation has a consistent format this section describes it as best as possible. It's recommended
+to check additional sections for examples.
+
+#### Layout
+
+The first thing in the configuration documentation should be a description of the area. This is promptly followed by the
+configuration heading (h2 / indent 2) which has an example full configuration.
+
+Under the configuration example each option in the configuration needs to be documented with its own heading 
+(h3 / indent 3). Immediately following the heading is a div with some stylized icons. 
+
+The body of the section is to contain paragraphs describing the usage and information specific to that value.
+
+
+**Example Stylized Icons:**
+
+```html
+<div markdown="1">
+type: string
+{: .label .label-config .label-purple } 
+default: example
+{: .label .label-config .label-blue }
+required: no
+{: .label .label-config .label-green }
+</div>
+```
+
+##### type
+
+This section has the type of the value in a semi human readable format. Some example values are `string`, `integer`, 
+`boolean`, `list(string)`, `duration`. This is immediately followed by the styles `.label`, `.label-config`, 
+`.label-purple`.
+
+##### default
+
+This section has the default of the value if one exists, this section can be completely omitted if there is no default.
+This is immediately followed by the styles `.label`, `.label-config`,
+`.label-blue`.
+
+##### required
+
+This section has the required status of the value and must be one of `yes`, `no`, or `situational`. Situational means it
+depends on other configuration options. If it's situational the situational usage should be documented. This is 
+immediately followed by the styles `.label`, `.label-config`, and a traffic lights color label, i.e. if yes `.label-red`, 
+if no `.label-green`, or if situational `.label-yellow`.