Fixes various issues in documentation:
- replaces HTML anchor tags in markdown headings by markdown heading IDs.
- replaces HTML linebreaks by newline commands
- replaces \htmlonly commands for image resizing by the width argument in \image commands
- uses more unique identifiers for references
- uses stable references for driver documentation
- fix broken links to external HTML documents
- replaces the TOC link in headers by a back to TOC link below each section
- replaces ``` fenced code blocks by ~~~
Since a number of applications rely on the existence of the BTN0_PIN definition, the BUTTON0_PIN definition has been renamed to BTN0_PIN to make the ESP32 boards compatible with these applications. However, for compatibility with earlier versions, BUTTON0_PIN is still defined as an alias of BTN0_PIN.
Instead of using the same MCU feature table in every board documentation, it refers to the MCU documentation. This makes it easier to maintain the MCU feature table.
According to the datasheet, SX1278 covers frequencies till 525MHz
and hence, cannot be used for the 868/915 MHz band. So swap both
chips.
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
