Release 0.6.0

Highlights:

• New feature: OTA zlib decompression (alternative to heatshrink)
• New feature: OTA delta updates (bsdiff + zlib)

Added

• .gitmodules: add miniz library
• .gitmodules: add bsdiff library
• .github: build modus_toolbox project in CI
• port: add read_current_image_at_offset() function, required to implement by ports
• fw_update: new option to decompress using zlib algorithm
• fw_update: new feature, delta FW updates
• scripts: add OTA scripts to compress and generate patch files
• docs: add Modus Toolbox to integration guide

Changed

• golioth_basics: change RPC method from "double" to "multiply"
• libcoap: update to tip of develop branch
• heatshrink: update to tip of develop branch, build without dyn mem allocation
• fw_update: internal restructuring, process blocks through a chain of functions
• config: for decompression, must select either heatshrink or zlib algorithm

Fixed

• shell: verify key is correct before accessing NVS
• port/linux: handle EINTR correctly in golioth_sys_sem_take()
• coap_client: allow for no block2 option in block req response, fixes single-block downloads
• examples/esp_idf: allow for up to 32 chars for wifi creds (was 31)