docs: theme config and list of theme templates (#116)

- Added theme configuration guide in README
- Added some theme templates
- Added list of theme templates in `themes/`

themes/catppuccin-frappe.toml

@@ -0,0 +1,19 @@
+border = "#ca9ee6"
+accent = "#81c8be"
+muted = "#737994"
+text = "#c6d0f5"
+text_sel = "#c6d0f5"
+key = "#ca9ee6"
+match = "#a6d189"
+desc = "#a5adce"
+desc_sel = "#c6d0f5"
+sel_bg = "#626880"
+sel_text = "#303446"
+scroll_info = "#ca9ee6"
+ghost_text = "#626880"
+sys = "#414559"
+sys_sel = "#ef9f76"
+hist = "#292c3c"
+hist_sel = "#81c8be"
+alias = "#414559"
+alias_sel = "#ca9ee6"