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-mocha.toml

@@ -0,0 +1,19 @@
+border = "#cba6f7"
+accent = "#94e2d5"
+muted = "#6c7086"
+text = "#cdd6f4"
+text_sel = "#cdd6f4"
+key = "#cba6f7"
+match = "#a6e3a1"
+desc = "#a6adc8"
+desc_sel = "#cdd6f4"
+sel_bg = "#585b70"
+sel_text = "#1e1e2e"
+scroll_info = "#cba6f7"
+ghost_text = "#585b70"
+sys = "#313244"
+sys_sel = "#fab387"
+hist = "#181825"
+hist_sel = "#94e2d5"
+alias = "#313244"
+alias_sel = "#cba6f7"