pull_request_template tell about rules (#580)

improve pull request template
- add info regarding processes
- add example regarding typo/spelling/grammar fix.

---------

Signed-off-by: Jan Kowalleck <[email protected]>

Author: jkowalleck

.github/pull_request_template.md

@@ -2,17 +2,23 @@
 Thank you for taking the time to develop and contribute a core enhancement or fix for a defect!
 
 We kindly request that you create pull requests only for things that have been discussed in a ticket first; exceptions may be made for spelling or grammar fixe.
+Read more about the process here: https://cyclonedx.org/participate/standardization-process/#working-model
+
 Please have the related ticket/issue ID ready. 
 If there is none, feel free to create a new ticket: https://github.com/CycloneDX/specification/issues/new/choose
+
 -->
 
 <!-- 
 
-Please provide a brief description of what this pull request intends to do and which ticket it fixes/closes.
-
+Please provide a brief description of what this pull request intends to do and which ticket it fixes/closes.  
 Example: 
-> As discussed in ticket #485, this PR adds Streebog to the hash algorithm enum. 
-> 
+> As discussed in ticket #485, this PR adds Streebog to the hash algorithm enum.
+>
 > fixes #485 
 
+In case this is for a spelling or grammar improvement, please provide a brief description.
+Example:
+> Fixe typo: color(AE) -> colour(BE)
+
 -->