Developer Portal on Mobile device looks strange

[georgik]

[f-hollow]

PR #425 added a quick fix to reduce the header's vertical size.

• The string Espressif Developer Portal in the header was reduced to Developer Portal
• The burger menu, search button, and language switch (also the hidden dark/light theme appearance) appears in the second row aligned to the right.

Follow-up actions

• It might be good to change the header from fixed (pinned to the top, the Blowfish theme is pretty unique in this regard) to scrollable as in most Hugo themes.
• We might want to create our own Devportal logo to do away with the string "Espressif Developer Portal".
• We can make a more thorough review and more sophisticated updates later.