Implement LF RFID emulation (#208)

* migrate code from old repo, not work
* fix emulation
* disable irq handling while RFID emulating
* add testcase

applications/lf-rfid/em4100.c

@@ -0,0 +1,68 @@
+#include "flipper_v2.h"
+
+void prepare_data(uint32_t ID, uint32_t VENDOR, uint8_t* data) {
+    uint8_t value[10];
+
+    // vendor rows (4 bit in a row)
+    value[0] = (VENDOR >> 4) & 0xF;
+    value[1] = VENDOR & 0xF;
+
+    const uint8_t ROW_SIZE = 4;
+    const uint8_t HEADER_SIZE = 9;
+
+    // ID rows (4 bit in a row)
+    for(int i = 0; i < 8; i++) {
+        value[i + 2] = (ID >> (28 - i * ROW_SIZE)) & 0xF;
+    }
+
+    for(uint8_t i = 0; i < HEADER_SIZE; i++) {
+        data[i] = 1; // header
+    }
+
+    for(uint8_t i = 0; i < 10; i++) { // data
+        for(uint8_t j = 0; j < ROW_SIZE; j++) {
+            data[HEADER_SIZE + i * (ROW_SIZE + 1) + j] = (value[i] >> ((ROW_SIZE - 1) - j)) & 1;
+        }
+
+        // row parity
+        data[HEADER_SIZE + i * (ROW_SIZE + 1) + ROW_SIZE] =
+            (data[HEADER_SIZE + i * (ROW_SIZE + 1) + 0] +
+             data[HEADER_SIZE + i * (ROW_SIZE + 1) + 1] +
+             data[HEADER_SIZE + i * (ROW_SIZE + 1) + 2] +
+             data[HEADER_SIZE + i * (ROW_SIZE + 1) + 3]) %
+            2;
+    }
+
+    for(uint8_t i = 0; i < ROW_SIZE; i++) { //checksum
+        uint8_t checksum = 0;
+        for(uint8_t j = 0; j < 10; j++) {
+            checksum += data[HEADER_SIZE + i + j * (ROW_SIZE + 1)];
+        }
+        data[i + 59] = checksum % 2;
+    }
+
+    data[63] = 0; // stop bit
+
+    printf("em data: ");
+    for(uint8_t i = 0; i < 64; i++) {
+        printf("%d ", data[i]);
+    }
+    printf("\n");
+}
+
+void em4100_emulation(uint8_t* data, GpioPin* pin) {
+    taskENTER_CRITICAL();
+    gpio_write(pin, true);
+
+    for(uint8_t i = 0; i < 8; i++) {
+        for(uint8_t j = 0; j < 64; j++) {
+            delay_us(270);
+            gpio_write(pin, data[j]);
+            delay_us(270);
+            gpio_write(pin, !data[j]);
+        }
+    }
+
+    gpio_write(pin, false);
+    taskEXIT_CRITICAL();
+}