feat: enhance ui using javascript in admin area

• bundle js using rollup
• add basic rollup config to bundle minified and browser compatible js
• use babel to transpile typescript files to js
• add markdown editor, html editor, dropdown and tooltip features using third-party packages
• integrate optimized inline svg icons from RemixIcon using svgo and a php helper
• add scripts in package.json to bundle icons, images, css and js
• update tailwind config to add purgecss lookups and typography plugin
• refactor views to add missing pages in user journey
• update admin's holy grail layout using css grid
• add static code checkers: eslint and stylelint
• update package.json scripts
• update DEPENDENCIES.md file to include rollup and popper
• set html in rss feed description fields
• update Podcast and Episode entities to add description_html attribute generated by parsing markdown to html using parsedown

#9 (closed)