Various improvements to the repository documentation #1395

Job	Run time
Compile the UX-less version of the app on Nano S+ for performance tests	1m 28s
Compilation for X, S+, Stax and Flex (nanox, $NANOX_SDK)	1m 40s
Compilation for X, S+, Stax and Flex (nanosp, $NANOSP_SDK)	1m 37s
Compilation for X, S+, Stax and Flex (stax, $STAX_SDK)	1m 52s
Compilation for X, S+, Stax and Flex (flex, $FLEX_SDK)	1m 52s
Performance report	4m 1s
Unit test	1m 17s
Tests on mainnet (nanox)	35s
Tests with the Python library and legacy Bitcoin app	45s
Tests with the JS library	1m 23s
Tests on mainnet (nanosp)	29s
Tests on mainnet (stax)	34s
Tests for rust client library	1m 58s
Tests on mainnet (flex)	30s
	20m 1s

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