[doc] Use consistent spelling/capitalization of names

Consistently use the following spelling for document formats,
programming languages, and names:

- Markdown
- Hjson
- JSON
- Verilog
- HTML
- GitHub
- CSS
- Python

Also avoid abbreviations:
- repo -> repository

Signed-off-by: Philipp Wagner <phw@lowrisc.org>
diff --git a/util/reggen/gen_selfdoc.py b/util/reggen/gen_selfdoc.py
index 49dd7df..7d80402 100644
--- a/util/reggen/gen_selfdoc.py
+++ b/util/reggen/gen_selfdoc.py
@@ -89,7 +89,7 @@
 Field names should be relatively short because they will be used
 frequently (and need to fit in the register layout picture!) The field
 description is expected to be longer and will most likely make use of
-the hjson ability to include multi-line strings. An example with three
+the Hjson ability to include multi-line strings. An example with three
 fields:
 
 ```hjson
@@ -234,7 +234,7 @@
         doc_tbl_line(outfile, x, None, validate.hwaccess_permitted[x][0])
 
     genout(outfile,
-           "\n\nThe top level of the json is a group containing "\
+           "\n\nThe top level of the JSON is a group containing "\
            "the following keys:\n")
     doc_tbl_head(outfile, 1)
     for x in validate.top_required: