docs: simplify internal docs links

Fewer links means less confusion.

- Merge doom-issue and doom-commit links into doom-ref (for auto-linking
  Issue/PR/commit references).
- Merge doom-module-source and doom-docs-source links into doom-source.
- Rename doom-report-issue to doom-report.
- Use '!' as the icon for module issues link.
- Remove doom-repo (replaced with "doom:*" in :lang org module).
- Add doomdir and emacsdir links to :lang org module.

modules/editor/file-templates/README.org

@@ -1,4 +1,4 @@
-← [[doom-module-index:][Back to module index]]               ↙ [[doom-module-issues:::editor file-templates][Issues]]  ↖ [[doom-module-source:editor/file-templates][Source]]  ± [[doom-suggest-edit:][Suggest edits]]  ? [[doom-help-modules:][Help]]
+← [[doom-module-index:][Back to module index]]               ! [[doom-module-issues:::editor file-templates][Issues]]  ↖ [[doom-source:modules/editor/file-templates/][Github]]  ± [[doom-suggest-edit:][Suggest edits]]  ? [[doom-help-modules:][Help]]
 --------------------------------------------------------------------------------
 #+TITLE:    :editor file-templates
 #+SUBTITLE: Fill the void in your empty files

modules/editor/file-templates/templates/org-mode/__doom-readme

@@ -92,12 +92,12 @@ the purpose of the module and the features/technology(ies) it provides.
 #
 # ALSO: Version headings should be linked to the respective heading in
 # docs/changelog.org.
-** [[doom-release:v21.12.0][v21.12.0]] [2021-12-30]
-*** [[doom-commit:a1b2c3d4][commit SUBJECT linked to github commit]]
+** [[doom-tag:][v21.12.0]] [2021-12-30]
+*** [[doom-ref:a1b2c3d4][commit SUBJECT linked to github commit]]
 commit BODY
-*** [[doom-commit:a1b2c3d4][commit SUBJECT linked to github commit]]
+*** [[doom-ref:a1b2c3d4][commit SUBJECT linked to github commit]]
 commit BODY
-*** [[doom-commit:a1b2c3d4][commit SUBJECT linked to github commit]]
+*** [[doom-ref:a1b2c3d4][commit SUBJECT linked to github commit]]
 commit BODY
 
 # If no changelog is available, use: