Add themes documentation

- Renamed all index.md to readme.md to make consuming the documentation
from the Github repo easier. VuePress treats index.md and readme.md the
same way when building the static pages.
- Added theme section overview documentation
- Added how to customize documentation
- Added custom style imports to support OpenBMC Web UI component
documentation to remove Bootstrap framework base styles that conflict
with the Vuepress theme
- Found occurrences of the word Sass in upper-case and changed to use
sentence case.

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: If5588f88a3d75761cc47e85a3fb0a582b31d373c
diff --git a/docs/.vuepress/styles/_bootstrap.scss b/docs/.vuepress/styles/_bootstrap.scss
new file mode 100644
index 0000000..31a5f34
--- /dev/null
+++ b/docs/.vuepress/styles/_bootstrap.scss
@@ -0,0 +1,34 @@
+// Removing reboot and type imports to resolve
+// conflicts with vuepress styles
+@import "~bootstrap/scss/functions";
+@import "~bootstrap/scss/variables";
+@import "~bootstrap/scss/mixins";
+@import "~bootstrap/scss/root";
+@import "~bootstrap/scss/alert";
+@import "~bootstrap/scss/badge";
+@import "~bootstrap/scss/breadcrumb";
+@import "~bootstrap/scss/button-group";
+@import "~bootstrap/scss/buttons";
+@import "~bootstrap/scss/card";
+@import "~bootstrap/scss/close";
+@import "~bootstrap/scss/code";
+@import "~bootstrap/scss/custom-forms";
+@import "~bootstrap/scss/dropdown";
+@import "~bootstrap/scss/forms";
+@import "~bootstrap/scss/grid";
+@import "~bootstrap/scss/images";
+@import "~bootstrap/scss/input-group";
+@import "~bootstrap/scss/list-group";
+@import "~bootstrap/scss/media";
+@import "~bootstrap/scss/modal";
+@import "~bootstrap/scss/nav";
+@import "~bootstrap/scss/navbar";
+@import "~bootstrap/scss/pagination";
+@import "~bootstrap/scss/popover";
+@import "~bootstrap/scss/progress";
+@import "~bootstrap/scss/spinners";
+@import "~bootstrap/scss/tables";
+@import "~bootstrap/scss/toasts";
+@import "~bootstrap/scss/tooltip";
+@import "~bootstrap/scss/transitions";
+@import "~bootstrap/scss/utilities";
\ No newline at end of file